246 Colonial Organisms. [March, 
in the spores of all plants from the Fungi to the Ferns, and sexual 
propagation arises through a combination of two cells produced 
by this secondary growth. 
As the gastrula seems to be the primitive form of thë many- 
celled animal, so we might reasonably look for some parallel 
typical form in plants. In all higher plants the leaf is the mos 
apparent fundamental form. Yet the leaf is the result of a com 
siderable degree of evolution, and is preceded in the lowest plants 
by a mere mass of undifferentiated cells which assumes no typi- 
cal form. There is no requirement of a digestive cavity to which 
the fundamental form of animals is due. This cell mass assumé 
the leaf shape in some of the Algæ. In the mosses the leaf bè 
comes more definitely organized, and still more so im the fems 
but gains its highest condition only in the phanerogams. The 
embryological development passes through conditions analogous i 
to those of animals. Birth consists in the extrusion of a singl 
cell which, after fertilization, develops into a cell colony, and sub 
sequently, in the higher plants, produces embryo leaves, stem 
root in its ovarian development. In all plants a mass 0 me 
ganized tissue represents the early cell colony, while the leaf 7 
the flower appear in the higher plants as the ultimate results ; 
vegetable evolution. But these higher plants are in puer Í 
sense individuals. They are colonies of but slightly $ e 
nated members. The mosses, the ferns and their cong’ ers, 
little more than leaf colonies. An Endogen is an organ! fal 
each of whose members is a single leaf. In the Exogen "i 
step of progression is made, and the individual m a 
colony is a group of leaves, attached alternately to an unbrane 
stem. pich 
In all plant colonies a stock-mass or stem is formet A T 
serves as a reservoir of nutriment and a vascular organ ii he 
mosses and lower ferns this stem lies under grout i steni 
germs which it produces unfold into colonies of individua Fl 
or leaves. The colonies are annually reproduced, and eat in $ 
something to the dimensions of the stock mass, which, i 
higher ferns, emerges from the ground, and gradusi a 
upwards into the air. This fern stem has no power of sel atid 
It is made up of the bases of old leaves, of vascular bu K zi 
serve to supply the new leaves with nutriment, and ch to l 
roots which grow abundantly from its sides, and add MIT i 
thickness. 
