ANATOMY OF TISSUES. TE? 
the rhizoids of the two plants are of equal rank, as well in 
respect to their place and manner of origin, as in their structure. 
To illustrate this we compare the thallus of Marchantia with 
the stem of any of the mosses. The former is a flattened, bi- 
lateral, dorsiventral body, whose point of vegetation is so 
situated with respect to the direction of the main growth of the 
plant as to insure this taking place in a horizontal direction 
and from one apex only. The rhizoids spring from the side of 
the thallus turned toward the earth or substratum. In the moss 
the main body of the plant is a radial organ composed of a 
complex of cells growing mostly from one extremity, while the 
rhizoids arise from a region directly opposite to the growing 
apex, fastening the plant to, and feeding it from the soil. 
The moss is a perfectly organized cormophyte. It does not, 
however, originate directly from the development of a single 
cell, but arises as a secondary stage of an asexually produced 
spore or cell. The egg-cell which it produces, on being fertil- 
ized, gives rise to a plant of extremely low morphological 
character ; we must therefore pass to the next class of plants to 
reach a root of different character, or a true root. 
In this class, namely the vascular cryptogams, the relation 
of the two generations changes and the plant that represents 
the species, that is the plant with stem and leaf, arises not from 
the asexually produced spore nor from any of its phases of 
growth, but from the fertilized egg-cell itself. Here then is the 
origin of the real or true root. It is an embryonic development 
of the fertilized egg-cell in such a way that one end of the main 
axis of the plant becomes the organ functioning as the root. In 
the early or embryonic form of such a plant, its organs may be 
described as two, axis and leaf; but the axis develops in such a 
way that it forms two organs, stem and root. Side organs of 
similar character are given off from both of these axes, those 
from the root being always roots, and those from the stem either 
roots or stems. In comparison with stem and leaf, the root is 
