xt7w3r0psg6h https://exploreuk.uky.edu/dips/xt7w3r0psg6h/data/mets.xml Prescott, Henry Paul. 1858  books b98-31-40188316 English J. van Voorst, : London : Contact the Special Collections Research Center for information regarding rights and use of this collection. Tobacco. Tobacco and its adulterations  : with illustrations drawn and etched / by Henry P. Prescott. text Tobacco and its adulterations  : with illustrations drawn and etched / by Henry P. Prescott. 1858 2002 true xt7w3r0psg6h section xt7w3r0psg6h 














                  THIS DAY IS PUBLISHED,
        Post 8vo, 544 pp., with Eight coloured Plates, price 18s.

                             THE

   AQUAR IAN NATURALIST;

            A MANUAL FOR THE SEA-SIDE.

                              BY

        PROFESSOR T. RYMER JONES, F.R.S.


  "To furnish the ordinary reader then in the most readable and attractive
way with full information on the construction, nature and habits of all the
marine creatures generally met with about our shores, is the general scope of
the Professor's work.
  " To al persons      we can unhesitatingly give the advice: take
Professor Jones's book with you, as in it you will find just what you want,
and no more-conveyed in language o       ht and pleasant, so chatty and
round-the-fire-of-an-eveningish (to coin a frightful long word), that when
you have got through the work, your only astonishment will be, that you
have acquired so much really scientific knowledge at so little cost, and with
labour so much like play."-Literary Gazette, August 21, 1858.



JOHN VAN VOORST, I PATERNOSTER ROW.

 













Svo, 3.. G3d., sewed,



TILE GROUND BENEATH US:

    ITS GEOLOGICAL PHASES AND CHANGES;

                            BEING
 THREE LECTURES ON THE GEOLOGY OF CLAPHAM AND
     THE NEIGHBOURHOOD OF LONDON GENERALLY.

                              BY

    JOSEPH PRESTWICH, F.R.S., F.G.S., ETC.


  "A popular exposition of the geology of the London neighbourhood, or,
to state it more generally, of the Tertiary Series. Seldom or never have we
met with any geological statement, intended for an ungeological audience,
which is at once so lucid, consecutive, and complete. No one can rise from
a careful perusal of these lectures without a thorough comprehension of what
is meant by the succession of the Tertiary strata, a good general idea of the
nature of their probable formation, and of the contemporaneous aspect of the
world around, and, what is perhaps yet more valuable, a clear notion of the
amount and degree of evidence on which these reconstructive theories rest.
Nothing tends more to the sound advance of popular, as well as scientific,
geology, than careful local monographs of this kind."-Guardian, August 4,
1 833.



JOHN VAN VOORST, 1 PATERNOSTER ROW.

 













    TOBAC CO
        AND

ITS ADULTERATIONS.

 This page in the original text is blank.

 












A14



f   -,



                AND   ITS







k WITH ILLUSTRATIONS DRAWN & ETCHEC



I



By



4



C      O T ILRY  RE     DEZSPATT ,

iK    OF THE INLAND REVENUE DEPARTMENT  



          LONDON

JOHN VAN VOORST, PATERNOSTER Row

           1858



4-

 This page in the original text is blank.

 











                  PREFACE.





THE following pages have been written for the pur-
pose of assisting Officers of the Government, and others
interested in the subject, in acquiring a knowledge of
the characters of unmanufactured and manufactured
Tobacco, and of enabling them to detect its impurities.


  Among the adulterations which have from time to time
been discovered in manufactured Tobacco, the follow-
ing substances may be named :-Leaves of RhAzbarb,
Dock, Burdock, Colitfoot, Beech, Plantain, Oak, and 1nm;
Peat-earth, Bran, Sawdu8t, Ala-rootlet8, Barley-meal,
Oat-meal, Bean-meal, Pea-meal, Potalo-starch, and Chi-
cory-leaves steeped in tar-oil.


  From the foregoing enumeration it will be evident
that the object ill view cannot be attained by the study

 


PREFACE.



of Tobacco alone, and that, as the adulterating ingre-
dients are for the most part derived from the Vegetable
World, the structural peculiarities of the roots, stems,
and leaves of other plants, and the forms of their con-
stituent elements, require to be carefully studied.


  The subjects illustrated have been selected from my
note-book, principally with reference to the known
adulterations of Tobacco. The leaves of some plants to
which Tobacco is allied have been selected for the pur-
pose of enabling the Student to compare their forms and
structure, others on account of some resemblance which
they bear to each other, and, as such, affording useful
examples in the method of analysis which the book is
intended to teach. A few leaves of plants possessing
poisonous or medicinal qualities have also been intro-
duced, in the belief that Students in Medicine who are
making microscopical study a branch of their pros
fessional education will find the volume of some use.
Collaterally, the Microscopist and the Physiologist may
feel interested in the forms and structure of the hair8
of leaves, whose uses in Nature's vast ceconomy science
has not yet explained.


  T o render the work more useful to those for whom it
is chiefly intended, a concise description of the eonstruc-



IV

 


PREFACE.



tion of the Microscope, and its Management in the Exa-
nination of some Vegetable Tissues, has been added.


  It has been my endeavour to dispense with scientific
terms as much as possible; but in doing so there is a
constant tendency to fall into a diffuse and indefinite
method of expression.  It is hoped therefore that the
reader unacquainted with scientific language will not
be scared by a few terms that may at first appear harsh,
but rather that he will court that familiarity with them
which a little patient study will be sure to bring.


  To Sir William Hooker, Director of the Royal Gardens
at Kew, and to Dr. Joseph Hooker, I am indebted for
the liberal supply of fresh specimens of leaves, &c.,
from which my analyses and drawings have been made;
to the latter gentleman especially my best thanks are
tendered for many useful hints on the subject of botani-
cal illustration.


   To Mr. John Pye, whose name is so honourably
associated with the best productions in the English school
of landscape-engraving, my grateful acknowledgments are
here offered for his valuable direction in the etching of
the Platcs,-friendly assistance which has contributed as
largely to any merit, they may possess, as it has lessened



V

 



PREFACE.



my labour and anxiety in producing them. Beauty of
delineation has been less aimed at than accuracy: some-
thing will be gained to the student if the freshness which
alone pertains to life-studies has been preserved.


  The authorities from whom information has been
derived have, in every instance, been carefully cited.
Where the name of Dr. Lindley appears, reference is
intended either to that author's 'Vegetable Kingdom,'
'Medical and (Economic Botany,' 'Elements of Botany,'
or ' School Botany,'-works which have been frequently
consulted.

                           HENRY P. PRESCOTT.
 St. John's Wood,
    July 1858.



vi

 











                  CONTENTS.





                      CHAPTER I.
                                                     Page
Introduction . ............... . I


                     CHAPTER II.

Leaves:-Form andi Venation .  . . . .    . . . .   .   5


                     CHAPTER III.

Vegetable Cells and Vessels, and their Contents  .  . .      12
      The Vegetable Cell.  . .  .  . . . . . . .      12
      The Cell-wall. . . . . . . . . .       . . .    12
      Cell-contents. . .   . . . . . . . . . .        14
      Forms of Cells and Vessels.. . . . .    . . .    15
      Secondary Deposits. . .   . . . . . . .     .   18


                     CHAPTER IV.

Anatomy of Plants .  . . .   . . . .    . . . . .     20
      Structure of the Root. . . . . . . . . .        20
      Structure of the Stem. .  . . . . . . . .       22
Heart-wood.                                                  2
      Beech-wood .25
      Mahogany-wood .25
      Pine-wood .26
      Logwood ..6........... . 26

 



CONTENTS.



Structure of Leaves



Tobacco
Tobacco (pure and adulterated) .
Thorn-apple
Deadly Nightshade
Potato
Burdock.
Butterbur
Coltsfoot
Chicory .  .  .  .  .  . .  .  .   .
Dandelion
Sunflower
Elecampane
Comfrev.
Dock.
Rhubarb .
Foxglove.
Mullein-High Taper .
Green Hellebore.-Stinking Hellebore
Plantain.



             32
             33
             36
             39
             41
             43
             43.
             47
             49
             .52
             .54
.  .
             38
             60
             62
             61
             66
             68
             71



CHAPTER V.



Starches   .  .
      Tous-les-mois
      Potato
      Rye   .
      Wheat
      Barlev
      Oat   .
      Tobacco
      Rice .
      Bean .
      Pea .
      Orris-root



........ . ..... 73
....... . ...... 76
........ . ..... 77
........ . ..... 78
........ . ..... 79
........ . .... 80
........ . .... 80
                 81
........ . ..... 81
    . ... .  . 82
    . ... .  . 82
  . .. .  .  .  82



CHAPTER VI.



The Microscope
      Construction



Page-
27



Villl



. . . . .

. . . . .
. . . . .
. . . . .

. . . . .
. . . . .



84
84

 



                    CONTENTS.                          ix
                                                      Plage
Forms of lenses  .  .  .  .  .  .  .  .  .  .  .  .   84
Action of lenses-. .  .  .  .  .  .  .  .  .  .  .    85
Focal length of lenses .  .  .  .  .  .  .  .  .  .   86
Simple Microscope   .  .  .  .  .  .  .  .  .  .  .   87
Compound Microscope    .    .  .  .  .  .  .  .  .    88
Spherical aberration of lenses. .  .  .  .  .  .  .   88
Decomposition of light-the prismatic spectrum  .  .   89
Chromatic aberration of lenses.  . .  .  .   . .  .   89
Correction for spherical and chromatic aberration   .  .    89



      Achromatic object-glass
      Eye-glass-field-glass
      Eye-piece
Illumination of objects
      Condenser.
      Side reflector
      Mirrors.
Mlanagement of the Microscope
      Impurities.
      Air-bubbles
      Position of the microscope
Examination of Vegetable Tissues
      Dissecting Microscope
      Dissection.
      Vertical sections of leaf-blade
      Epidermis of midrib, veins, ar
      Ve rtical sections of wood
      Examination of samples of sni
      Chemical reagents and their u
      Examination of wood-structur



  ....... . . . ....... 90
  , .   .  .  .  .  .  .   90
  .......... . .   .  .  ... 90
  .......  .  .  .  ...... 90
  ...........  .  .  .  ... 90
  ...........  .  .  . ... 90
                           91
  ..........  .  .  .  ... 92
  ..........  .  .  .  .... 93
  ..........  .  .  .  ..... 94
                           93
  ..........  .  .  . . ..    9.5
  ..........  .  .  .  ..... 96
  ..........  .  .  .  .... 96
  ..........  .  .  .  ... 98
id leaf-blade . . . .      99
.......  .  .  .  ...... 100
'if .  .   .  .  .  . .   100
ises.  .   .  .  .  .  .  101
es, &c..  . . . . . 102



                       CHAPTER VII.
History, Use, Cultivation, and Manufacture of Tobacco
      History and use of Tobacco in England.
      Cultivation of Tobacco.
      Manufacture of Tobacco for smoking, chewing, an(d
        snuffing.
      Raw and Manufactured Tobacco imported into En-
        gland, and exported



105
106
113

119



1 2:1

 This page in the original text is blank.

 








                   TOBACCO


                           AEND


         ITS ADULTERATIONS.





                      CHAPTER I.

                      INTRODUCTION.

THE various and beautiful organic structures contained in the
Vegetable Kingdom have, many of them, important relations to
the necessities and the luxuries of mankind. Foremost among
these may be considered the all-important one of food, which
vegetation furnishes, either directly to man himself, or indi-
rectly to him, as the nourishment of those animals which he
consumes. Cotton, a vegetable product; coal, also of vegetable
origin; medicinal herbs, with their thousand applications to the
alleviation of human pain; and tobacco, the narcotic indul-
gence, in a greater or less degree, of nearly the whole civilized
globe, are so many illustrations of the manifold uses of plants
and their products.
  Not less wonderful than the beauty and symmetry of the
outward forms of plants, are the wide distribution and enormous
amount of organizing forces which they possess, enabling them
(unlike the members of the animal kingdom) to throw out new
                                               B

 


TOBACCO AND ITS ADULTERATIONS.



tissues from any part almost of their structure, and, by the
rapidity with which these increase, to yield to man and animals
an ample supply of useful material.  Dr. Desaguliers, a French
philosopher, ascertained, by careful experiment, that a turnip
seed increased fifteen times its own weight in a minute, and the
root fifteen thousand times its original weight per day.
Familiar instances of the enormous amount of vital force pos-
sessed by the seeds of plants are seen in the growth of them in
moistened flannel, a medium sufficient to elicit this latent energy,
and, for a time, to sustain it.  The germination of grain in the
malting process is another instance in which water and air exert
a similar influence. The readiness with which plants throw out
their tissues from almost any part of their structure, to form
new plants, is taken advantage of by the gardener in his opera-
tions of " cuttingy " and "grafting :" in that of layering, as it is
technically termed, he repeats a natural process constantly occur-
ring during the growth of the Strawberry plant.
  Nature does not perhaps exhibit a grander phenomenon for
contemplation than the silent appropriation and assimilation by
plants, of those gases which, either exhaled from the lungs of
animals, or as the products of fermentation and putrefaction of
decaying animal and vegetable matters, are continually floating
in the atmosphere and prove injurious to animal life. Among
these are carbonic acid and ammonia. In the assimilation of
the carbon, and liberation of the oxygen of the carbonic acid
by the leaves of plants, they may be considered so many labo-
ratories wherein this gas is resolved into its constituent ele-
ments-a result which the profoundest chemist strives in vain
to accomplish; in yielding oxygen, they return to the air its life-
sustaining element.  In their outward aspect, beauty of form,
of texture, and of colour combine to render them most at-
tractive objects.
                   Lindley's Elements of Botany.



2

 


I N TRODUCTION.



  There is not a plant that grows but has its leaves formed on
a fixed and definite plan; and in each plan may be distinctly
traced a peculiarity of its own. The shape which leaves assume
is, in some instances, of so marked a character as to enable
us to predict with certainty the poisonous properties of the
plant which has produced them; whilst the arrangement of
their veins is a no less certain index of the internal structure of
the stem on which they have grown, and even of the seed from
which their parent plant has been derived. Thus the oak-leaf
and the acorn alike inform us of the arrangement of the minutest
fibres within the giant stem which has supported and matured
them.
  When the structure of a leaf is examined, it is found to be
covered externally with a delicate transparent skin, or epidermis,
on which are thickly clustered extensions of its cellular elements
in the form of hairs, so minute that the quickest sight can only
detect their presence as a soft downy substance, but in which
the microscope reveals to us a forest of forms as various as the
leaves on which they grow, and withal as true as they to their
appointed symmetry. Lying scattered among these, again, are
the pores (stornates), through which air and gases find their way
to or from the interior of the leaf; and beneath these, cavities
which conduct them to the inner laboratory, built up of nuin-
berless cells, in which they are decomposed or absorbed.
   On examining the substance of some leaves, minute crystals,
truly geometrical in their forms, are seen suspended in beautiful
clusters from the ceiling of a cell, or lying in compact or scat-
tered masses on the floor within it, in the form of delicate
needle-shaped bodies, which become beautifully tinted with
variegated colours under the action of polarized light.  Or,
again, myriads of starch-granules, differing in their forms ac-
cording to the plant in which they are found, lie stored in the
cells of their leaf-stalks, steins, and roots.  From the extreme
                                                  B 2



3

 




-I           TOBACCO AND ITS ADTJLTERATIONS.

delicacy of all these bodies, they elude any mechanical efforts to
destroy their structure, however finely either leaf, stem, or root
may be divided.
  Taking, then, the definite characters which the externalform
and venation of leaves afford, and those structural peculiarities
of them, and of the stems and roots of plants, which the micro-
scope exhibits to us, it will be seen that there exists abundant
evidence of what is, and of what is not, "Tobacco," and that
if, by the substitution of the spurious for the genuine, our senses
are at times imposed upon, it is because we have neither exa-
mined nor studied those signs which here, as in her other
works, Nature offers continually to our view, serving as infallible
guides in the search after Truth,-and, it may be added, evi-
dences of that Power and Wisdom which framed the heavens
and the earth.

 



LEAVES :-FORIM AND VENATION.



                        CHAPTER II.

             LEAVES:-FORM AND VENATION.

                      PLATES III. & IV.

LEAVES form the respiratory and digestive apparatus of the
plant.  Their position on the stem is such as enables them to
expose a large surface to the action of the sun, light, and air;
and the numerous pores (stomates) with which their surfaces are
furnished allow them to exhale gaseous matters freely, as well
as to aerate the juices conveyed to them from the stem.
  A leaf consists of two parts: a flat, expanded portion called
the blade, or lamina (1, FIG. 3); and the leaf-stalk, or petiole (p).
The blade of the leaf is its principal portion, and its margin,
or boundary, defines the shape of the leaf.
  Exceptions to this rule occur in cases where the outline of the leaf is
very irregular, or deeply cut, such for instance as in the leaf of Thorn-apple
(PLATE XV.). In defining the form of such a leaf, it is usual to consider
an imaginary line bounding its extreme points, called a circuumscription.
In this sense the leaf is said to have an ovate form.

  The lainina, or blade, has two faces: the upper one, when the
leaf is in its natural position, is turned, more or less, towards
the sky; the lower towards the earth.   The base of the leaf is
that part of it to which the stalk is attached, when present, or
by which the leaf itself is joined to the stem. The point of the
leaf is opposite to the base. The blade of the leaf is traversed by
numerous lines, forming, as it were, a framework on which it is
stretched; these are most prominent on its under surface, and
are called, according to the degree of their prominence, ribs,
veins, and nervures. When one vein extends from the base to



5

 


TOBACCO AND ITS ADULTERATIONS.



the point of the leaf, dividing the blade into two equal, or nearly
equal parts, it is called a midrib (m, FIG. 4).
  The venation of leaves is a term applied to the branching of the
rib or ribs, veins, and nervures, through the blade; and is either,
  PARALLEL-VEINED-when the veins proceed from the base to
the point of the leaf in a parallel direction (FIG. 1).
  CURVINERVED-when the principal veins run in a curved
direction from the base to the point of the leaf. Ex. Plantain
(PLATE XXXVI.).
  RETICULATED, or net-veined-when the veins and nervures
branch laterally from the rib or ribs, through the blade of the
leaf, the primary veins not reaching to the margin (FIGS. 3, 4).
  FEATHER-VEINED-when a prominent midrib, or vein, gives
off other (primary) veins laterally, which go directly to the
margin of the leaf (FIGS. 9, 14).
  RADIATED-when the principal ribs or veins radiate from a
common point of the leaf-stalk, or base of the leaf (FIGS. 7, 15).
  Terms defining the forms of leaves are applied-1. to their
general outlines; 2. to their bases; 3. to their points; 4. to their
maryins.
  ENrIRE LEAVES are those whose margins are continuous and
uninterrupted (FIG. 2).
  DIvIDED LEAVES have their margins cut into various forms,
either regularly or irregularly (FIGS. 9, 29). When these divi-
sions extend deeply into the leaf, from the margin inwards, the
leaves are termed lobed (34, 35).
  COMPOUND LEAVES are those having two, or more, separate
leaflets (pinna), with a stalk common to all of them. Ex. Po-
tato (PLATE XVII.).
  1. SIMPLE LEAVES, whose venation is either parallel, reticu-
lated, feather-veined, or radiated.
  The forms of such leaves in their general outline are usually
designated either by a real or supposed resemblance to some



6

 



LEAVES:-FORM AND VENATION.



geometrical or other figure. Thus there are on PLATE Ill.,
FIG. (1) linear; (2) lanceolate; (3) oblong; (4) ovate, or egg-
shaped; (5) obovate, with the narrow end to the stalk; (6) oval,
or elliptical; (7) roundish; (8) reniform, or kidney-shaped;
(9) cordate, or heart-shaped; (10) obcordate, with the narrow
end to the stalk; (11) cordate-acuminate, or heart-shaped, with
a lengthened narrow point; (12) sagittate, shaped like an arrow;
(13) hastate, shaped like a halbert; (14) spathulate, shaped
like a spatula; (1 5) peltate, shield- or target-shaped; (16) gub-
ulate, or awl-shaped; (1 7) acerose, needle-shaped; (18) angu-
lar; (19) triangular; (20) cuneate, wedge-shaped; (21) ovate-
lanceolate; (22) oblique, or unequal-sided; (23) truncate, ter-
minating abruptly; (24) auriculate, having a pair of small ears
or lobes; (33) lyrate, shaped like a lyre.
  The forms of the bases of leaves, when specially referred to,
are designated as perfoliate, or perforated by the stem (FIG. 25);
(26) decurrent, when the blade of the leaf is continued down
the stem in a broad or narrow strip; (27) connate, when the
bases of two leaves are united; (28) amplexicaul, or embracing
the stem; (11) cordate; (21) ovate; (5) attenuated, or length
cned; (22) oblique.
  The points of leaves are also distinguished as acute (FIG. 2);
acuminate, still more acute; emaryinate, or notched inwards (6);
mucronate, when tipped with a sharp spine (20); obtuse, rounded
at the point (3); cuspidate, or tapering to a stiff point gradually
(1 1).
  The margins of leaves are entire (FIGS. 1, 2, 3), or divided
(7, 9).
  When the divisions are small and rounded, the leaf has a
crenated margin (FIGS. 7, 9); dentate, or toothed (11). When
the extremities of the dentations point towards the apex of the
leaf, the margin is serrated (4, 14) ; retroserrate, when they
point to the base. When such divisions are again divided, they



7

 



TOBACCO AND ITS ADULTERATIONS.



are douhly-demtatc, or doubly-semrate (29), or irregularly-8er-
rate, &c.
  2. LOBED LEAVES with feather-veined venation are called
piinnatifid (FIG. 30); pinnatisect (31) denotes a Btill greater
division of the margin, extending nearly to the midrib of the leaf;
bipinnatifid (32), when these divisions are again divided.
  A runcinate leaf is a form of the pinnatifid, 'in which the
divisions of the margin are shaped like the teeth of a large saw.
Exs. Chicory (PLATE XXIII.); Dandelion (PLATE XXIV.). The
leaf of Thorn-apple (PLATE XV.), in which the divisions of the
margin alternate in tooth-like projections and rounded curves,
is called sinuated.
   3. LOBED LEAVES with radiated venation are known        as
jialmifid or palmisect (FIG. 34); the prefix palmi denoting the
form of venation as radiated, in the manner of the fingers of the
human hand. AW'hen the divisions extend still further, they are
distinguished as tri-lobed, quinque-lobed (35), &c.
  4. COMPOUND LEAVES with feather-veined venation are called
pinnate, and are more closely defined by the number of pairs of
leaflets (pinnk-) of which they are composed. If of one pair
only, unjugate (FIG. 36); if of many, multtjugate (37, 38).
When each entire leaflet is composed of several small ones (37, 1),
the leaf is bipinnate (37).  Tripinnate is a term applied to bi-
pinnate leaves in which the leaflets are again pinnate.  When
the division of the leaf into leaflets extends still further, it is
called decompound (41). Equally-pinnate is a term applied to
compound leaves terminating in a pair of leaflets (37); unequally-
pinalte, if terminating in one (38).  When the leaflets alternate
with each other (38), the leaf is said to be alterni-pinnate; or
Interruptedly-pinnate, when some of the leaflets are   much
,rnaller than the others.  Ex. Potato (PLATE XVII.).   Conm-
pound leaves are also designated as ternate (29).
   5. COMPOU-ND LEAVES with radiated renation are known as



8

 



LEAVES:-FORM AND VENATION.



palmate, digitate, ternate (FIG. 10), qUinlate, or septenate (39);
these last terms defining the number of their leaflets as either
3, 5, or 7, joined to the stalk at one point.
  Pedate leaves are such as have their lateral leaflets again
divided into segments. Ex. Hellebore (PLATES XXXIV. &
XXXV.).
  THE ATTACHMENT of leaves to the stein is either by a stalk, or
(when this is absent) by the midrib, when they are said to be
sessile. Ex. American Tobacco (PLATES I. & XI.).
  THE POSITION of leaves an the stem is either opposite, alternate,
or in whorls or verticils.
  OPPOSITE leaves (PLATE IV. FIG. 42) are grouped in pairs at
the extreme points of any diameter of the stem.
  ALTERNATE leaves are placed separately at different heights on
the stem (FIG. 4.0). Ex. Tobacco.
  WHORLED, or verticillate, is a term applied to the position of
three or more leaves, placed at different points of the stem, in
the same plane (FIG. 43).
  Variations in the forms of leaves on the same plant are con-
tinually occurring, the leaves situated at the base of a stem
having for the most part more strongly-developed characters
than those found on any other part of it. The reason of this will
be readily understood on reflecting that the lowermost leaves are
not only of older growth, but that heat, light and air being
essential to their existence, their vital activity is exerted in that
direction from whence these proceed, and from the effects of
which the leaves disposed on the stem above serve to shade them.
Barley seeds, grown in earth, and placed in the darkened recess
of a chimney-corner, will, on germinating, bend their leaves for-
ward in the direction of the least ray of light. This and manv
other experiments prove the value of the solar rays to plants; and
repeated observation has confirmed their disposition to move
towards the sun. Botanists, therefore, when defining the forms



9

 


TOBACCO AND ITS ADULTERATIONS.



of leaves of many plants, refer to them either as radical leaves,
stem leaves, or floral leaves. The Tobacco and Dock plants
(PLATES I. & XXIX.) furnish examples of the variations here
alluded to.
  The texture of leaves, more especially of their blades, is con-
siderably modified in their outward aspect, both by their vena-
tion and the presence or absence of hairs or glands.  A broken
surface, by reflecting less light to the eye, assumes a rougher
texture and a darker colour; on the other hand, leaves whose
outer coverings are of a waxy nature (e. g. Laurel), and conse-
quently with more or less polished surfaces, have a brilliant and
sparkling appearance.
  The presence of hairs in any quantity on a leaf, will give,
according to their nature, the soft downy texture of the under
surface of the leaf of Coltsfoot, the roughness of the Potato
leaf, or the prickly character of the leaves of Sunflower and
Comfrey.   The Tobacco leaf, both in its natural and cured
conditions, is peculiarly sticky to the touch, owing to the easy
fracture of its numerous glandular hairs, which discharge their
contents: the immense hydraulic pressure to which the cured
leaves are submitted in packing them for exportation, is, simi-
larly, the cause of that peculiar greasy appearance which they
assume on the application of moisture previous to their manu-
facture.
  Terms which explain themselves, such as elastic, brittle, suc-
culent, leathery, are applied to those conditions of the leaf which
depend for their peculiar characters on the form and structure of
the venation and blade, the predominance in either part of cellular,
fibrous, or vascular tissues, and the character of the epidermis.
In their green state, the leaves of Elecampane (PLATE XXVI.)
furnish examples of strength afforded by fibrous tissue in the
midrib and veins.  The garden Cabbage leaf has a succulent
midrib and veins, and the blade partakes of both the leathery



10

 



               LEAVES:-FORM AND VENATION.                   11

and brittle characters.  When young, the cellular tissue pre-
dominates in this leaf, and in others that form our vegetable
food; but with age the fibrous tissue becomes more abundant,
making them " stringy," and consequently less palatable.
  Time produces other changes in the tissues of the leaf, as the
plant grows to maturity. Its epidermis thickens, the cells form-
ing its substance gradually harden, and their contents change
their colour from green to some shade of yellow, red, or brown;
at the same time starch, and matters partaking of a resinous
character, are formed, whilst the tissues through which the
crude sap found its passage to the leaves become stopped up by
organic matters deposited within them, circulation is prevented,
their functions cease, and the leaf falls.

 


TOBACCO AND ITS ADULTERATIONS.



                      CHAPTER III.

VEGETABLE CELLS AND VESSELS, AND THEIR CONTENTS.

                          PLATE V.

EXCEPTING among the lower forms of vegetation, and the minute
parts of the structures of some flowers, the unassisted eye can
readily distinguish the forms of the different organs of plants.
To obtain a knowledge of their anatomical structure requires the
use of a microscope, and special treatment of those parts which
form the subjects of inquiry. This instrument not only exhibits
to us their internal anatomy, but, in many cases, reveals those
phenomena of life which form the subject of the Physiologist's
researches.
  The examination of any portion of a plant, either from the
root, stem, leaves, or flowers, shows that it is composed of an
aggregation of cells and vessels.
  The Vegetable Cell is described by Vegeto-physiologists as a
minute and perfectly closed sac, or vesicle, formed by a very
transparent solid membrane, the cell-wall (FIGs. 1 wv, 7 w).
  Among things evident to the unassisted sense of sight, a closed and
inflated bladder, in which the skin represents the cell-wall, and the
enclosed space that of the cell-cavity, has, not inaptly, been chosen as an
illustration, on a large scale, of a vegetable cell, as revealed to us by the
microscope.
  This sac, or vesicle, has certain organizable matters contained
within its cavity-the cell-contents (FIG. 1, a, b, c), on which its
life and development depend.
  The Cell-wall. -The permeability of the cell-wall is a necessary



12

 


VEGETABLE CELLS AND VESSELS.



condition of the cell in performing the functions of absorption and
transmission of fluids and gases: it would appear that it is only
when it becomes charged with secretions partaking more or less
of the solid form, that such functions cease to be performed by it.
  Endosmose, an action which is induced whenever two liquids
of different densities, capable of mixing with each other, are
separated only by a membranous partition, is readily admitted
of by the cell-wall, which thus exerts an influence on the life of
the cell as an individual organism, collecting and distributing its
fluid contents, and determining the relation between them and
the contents of the cells by which it is surrounded. Endosmose
is also brought into play by the different densities of the fluid
matters contained in the cells of the roots of plants, and in the
soil through which they ramify.
  Capillarity, another physical force, is exerted by certain
organs largely developed in most vegetable tiss