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mode of reproduction in these plants of lower grade, 
we might have drawn the line of demarcation some- 
what differently. For, while the higher flowerless 
plants, such as the equisetums, the club-mosses, and 
ferns, do not essentially differ from the lower flower- 
ing plants in the structure and composition of their 
stems, &c., consisting as they do of all the kinds of 
elementary tissue (except perhaps the laticiferous), 
the mosses, and all below them in the series, are 
wholly composed of cellular tissue. If we were to 
make this distinction the basis of classification, as 
proposed by De Candolle, we should have two pri- 
mary divisions in the form of Vascular and Cellular 
plants ; the latter comprising the mosses, hepatice, 
lichens, sea-weeds, and fungi, which are entirely 
composed of cellular tissue, as well as flowerless. 
But another, and perhaps more natural division may 
be effected still lower in the series. For the mosses, 
although cellular, agree with the orders of higher 
grade in having regular stems, which grow upwards 
by means of buds, and are symmetrically clothed with 
distinct leaves: while the lichens, sea-weeds, and 
fungi, the most imperfect of vegetables, present no 
distinction into stem, root, and leaves, no polarity, 
or growth in two opposite directions, no buds, and 
no organs which are even analogous to flowers. 
Their homogeneous tissue often tends to the forma- 
tion of flat, more or less definite expansions, which 
is the nearest approach to any thing like leaves; in 
which their spores, mere vesicles or little masses of 
cellular tissue, are embedded. Hence they are 
termed Thallophytes. If the line of primary division 
be drawn in view of these important distinctions, as 
prepesed by Unger and Endlicher, the vegetable 
kingdem will be separated into two great, but un- 
equal series, viz., Ist, the Cormophytes, or Stem- 
growing plants, —those with a distinct axis of growth, 
elongating downwards into roots, and upwards by 
means of buds into stems, provided with leaves, and 
with reproductive organs analogous to flowers; and 
2d, the Thallophytes, which are stemless, rootless, 
leafless, and in every sense flowerless. But it will 
perhaps be found more convenient to retain the 
equally natural primary division into Flowering and 
flowerless plants, as already proposed; which are 
synonymous with the older, and not very objection- 
able names of Phenogamous, or Phanerogamous, and 
Cryptogamous plants. 
In this view, the series of Flowerless plants will 
naturally subdivide into two classes; the first em- 
bracing those with a stem, or distinct axis of growth, 
usually clothed with leaves; such as the ferns, club. 
mosses, mosses, &c.; which, as their stems usually 
grow by elongation from the apex solely, and have 
little or no provision for increase in diameter, have 
been termed Acrogens ; that is, point-growers: the 
second comprising the Thallophytes above-mentioned, 
which exhibit no such distinction of parts, and which, 
for the sake of uniformity, may be called Thallogens. 
The great series of Flowering or Phenogamous 
plants presents, as to the stem, two distinct kinds of 
structure and growth, the Hxogenous and the Endo- 
genous ; leading at once to a division into two classes, 
viz., the Hxogens or Outside-growers, and the Endo- 
gens or Inside-growers. ‘The embryo of Exogens is 
provided with a pair of cotyledons, that of Endogens 
with only one; whence the former are also termed 
Dicotyledonous, and the latter Monocotyledonous 
plants,—names introduced by Jussieu, the father of 
this branch of botany. There are other marks, more 
or less characteristic of these two classes; particu- 
larly the netted-veined leaves of the former, which 
usually fall off by an articulation, and the parallel- 
veined or nerved leaves of the latter, which decay 
without falling. 
There is, however, a group of Exogenous plants 
(of which the pines, firs, yew, &c., are representa- 
BOTANY. 
which differs from all the rest in having the ovules 
and seeds naked, instead of enclosed in an ovary or 
pericarp; and, as a set of spurious Endogenous plants 
(the cycas and zamia) accord with them in this re- 
markable particular, they are together deemed to 
form a third, although much smaller class, with the 
name of Gymnospermous (that is, Maked-seeded) 
plants, or Gymnosperms. 
There is still another small group of very strange 
parasitic plants, which seem to form a connecting 
link between Endogens and the lowest grade of 
Flowerless plants, or Thallogens; inasmuch as they 
are almost wholly composed of cellular tissue, and, 
although producing flowers, and those too, in one 
instance (that of the far-famed Rafflesia), of im. 
mense size, yet their ovaries are filled with spores 
instead of seeds. Hence they are considered to form 
the fourth and lowest class of Flowering plants, and 
have been named Rhizanthee or Root-flowering plants, 
as well as Sporogens, in allusion to their singular 
peculiarity. 
These four classes of Flowering plants may there- 
fore be characterized as follows :— 
Class I. Exocrns, or Dicotyiepons. Structure 
of the stem exogenous. Seeds ina peri- 
carp. Embryo with two cotyledons,— 
Leaves netted-veined. 
Class II, GymnosperMs. Seeds naked. Embryo 
with two or more cotyledons. 
Class III. ExpocEns, orMonocoryLepons. Struc- 
ture of the stem endogenous. Seeds in 
a pericarp. Embryo witha single coty- 
ledon. Leaves usually parallel-veined. 
Class IV. RuizantTus, or Sporocens. Structure 
mostly cellular. Pericarp containing 
spores instead of seeds. Embryo none. 
—Parasites. 
The two classes of Flowerless plants being added, 
the mutual relationship of the whole may be com- 
pletely expressed by disposing them, as it were, cir- 
cularly, in the following manner :— 
Exogens Endogens 
Gymnosperms Sporogens 
Acrogens Thallogens 
The Gymnospermous plants being nearly related on 
the one hand to Exogens or the highest Flowering 
plants, and on the other to the Acrogens or highest 
Flowerless plants, as will hereafter more fully ap- 
pear ; while the Sporogens are equally allied to the 
Endogens or lowest class of Flowering plants, and to 
the Thallogens or lowest Flowerless plants. The 
student will remark the impossibility of arranging 
even these six classes in a lineal series, so that each 
shall stand between the two to which it is particu- 
larly related. Thus, if the order be, 1. Exogens, 
2. Gymnosperms, 8. Endogens, 4. Sporogens, 5. 
Acrogens, 6. Thallogens (which is the consecutive 
series from the highest to the lowest grade), we fail 
to indicate the alliance of Gymnosperms to Acrogens, 
and of Sporogens to Thallogens. If the series be, 
1. Exogens, 2. Endogens, 3. Sporogens, 4. Gymno- 
sperms, 5. Acrogens, 6. Thallogens ; the Sporogens 
are still widely separated from the Thallogens, 
while they are brought next to the Gymnosperms, to 
which they are not allied; and two classes intervene 
between the latter and Exogens: similar obstacles 
stand in the way of any other lineal disposition. 
The leading characters of all the classes may also 
tives), belonging to the lower end of the series, 
be analytically expressed in the following manner :— 
eae 
