310 
LINDLEY S VEGETABLE KINGDOM. 
eacli other (P rotoccocus, Uredo), or united into 
simple threads (Conferva, Monilia), are suc- 
ceedtd by others in which the threads collect 
into nets (Hydrodictyon), or plates (Ulna), or 
the cells into masses (Laminaria, Agaricus) ; 
peculiar organs make their appearance, and at 
last, as the complication of structure increases, 
a leaf and stem unfold as distinctly limited 
organic parts. 
" Those simpler plants which exist without 
the distinction of leaf and stem, are also desti- 
tute of flowers ; they are equally without the 
breathing pores so abundantly formed in the 
skin of more complex species, and they multi- 
ply by the spontaneous formation in their 
interior, or upon their surface, of reproductive 
spheroids called spores. Among the many 
names that Botanists have given such plants, 
that of Thallogens is here preferred. A 
thallus is a fusion of root, stem and leaves, 
into one general mass ; and that is much the 
nature of these elementsof Vegetable structure. 
" Beyond Thallogens are found multitudes 
of species, which like the former are not 
furnished by nature with flowers, but which 
otherwise approach closely to the higher forms 
of structure, occasionally acquiring the stature 
of lofty trees. They have breathing pores in 
their skin ; their leaves and stem are distinctly 
separated ; in some of them, those spiral 
threads which form so striking a portion of 
the internal anatomy of a more perfect species 
exist in considerable abundance ; and finally, 
they multiply by reproductive spheroids, or 
spores, either formed without the agency of 
sexes, or, if the contrary shall be proved, at 
all events not possessing bodies constructed 
like stamens on the one hand and embryos on 
the other. Their stein, however, does not 
increase in diameter ; it only grows at the end, 
and hence it has given to such plants the name 
of Acrogens. 
" The changes which thus occur in the races 
of Thallogens and Acrogens represent the 
progress of development in the remainder of 
the Vegetable Kingdom. A sphere, called a 
pollen grain, protrudes a tube into a soft pulpy 
receptacle in the interior of an ovule ; there 
the new plant takes its birth, at first in the 
form of a cell, which by degrees forms a thread 
(the suspensor), then generates a cellular mass 
(the young embryo), and eventually becomes 
a mass of cells arranged in the form of stem 
and leaves (the perfect embryo, with its coty- 
ledons, radicle, and plumula). But this is not 
the end of growth ; it is rather the beginning. 
A loftier destiny awaits such plants ; flowers 
are to be formed, seeds to be fertilized, and this 
is to be effected by a complex apparatus un- 
known in Acrogens or Thallogens. 
" Foremost among the more perfect races 
comes a most anomalous collection of species, 
called RmzoGENS, or Rhizanths. These plants," 
leafless and parasitical, have the loose cellular 
organization of Fungi ; a spiral structure is 
usually to be found among their tissue only in 
traces. Some of them spring visibly from a 
shapeless cellular mass which stands in place 
of stem and root, and seems to be altogether 
analogous to the thallus of Fungi ; and it is 
probable, that they all partake in this singular 
mode of growth. Their flowers are like those 
of more perfect plants ; their sexual apparatus 
is complete ; but their embryo, which is not 
furnished with any visible radicle or cotyledons, 
appears to be a spherical or oblong homo- 
geneous mass. Rhizogens seem, in fact, of an 
intermediate nature between Fungal Thallogens 
and Endogehs. 
" The remainder of the Vegetable Kingdom 
consists of plants having flowers, and propa- 
gated by seeds ; that is to say, by bodies 
procreated by the mutual action of two mani- 
fest and undoubted sexes. Such plants are 
therefore called Phoenogamous or Sexual. 
" Sexual plants are themselves divisible into 
two unequal masses. Of these masses one 
consists of species whose germination is endo- 
rhizal, whose embryo has but one cotyledon, 
whose leaves have parallel veins, and whose 
trunk is formed of bundles of spiral and dotted 
vessels guarded by woody tubes ; which bun- 
dles are arranged in a confused manner, and 
are reproduced in the centre of the trunk. 
These are Endogens. 
" The other mass is composed of innume- 
rable races having an exorhizal germination, 
an embryo with two or more cotyledons, leaves 
having a net-work of veins, and a trunk 
consisting of woody bundles composed of 
dotted and woody tubes, or of woody tubes 
alone, arranged around a central pith, and 
either in concentric rings, or in a homogene- 
ous mass, but always having medullary plates, 
forming rays from the centre to the circum- 
ference, and reproduced in the circumference 
of the trunk, whence their name of Exogens. 
" Among Exogens there are, however, two 
totally different modes in which the influence 
of the pollen is communicated to the seed. 
The larger part of this great class consists of 
plants provided with the apparatus called style 
and stigma, through which pollen-tubes are 
introduced into the ovary during the act of 
fertilization. But others are so constructed 
that the pollen falls immediately upon the 
ovules, without the introduction of any inter- 
mediate apparatus ; a peculiarity analogous to 
what occurs among reptiles in the Animal 
Kingdom : and, as was to have been anticipated, 
the plants in which this singular habit occurs 
prove, upon being collected together, to form 
a group having no direct affinity with those 
among which they had been previously assc- 
