84 ELEMENTS OF PLANT ANATOMY. 
the elements of plant anatomy it is not considered practicable 
to take up the details of the anatomical structure of the plants 
of the less conspicuous generation. 
Thus, in the present class, the thallus represents what is 
termed the first generation, or the one bearing the sexual 
organs and producing the egg-cell, which has not the ability to 
germinate until after it has been fertilized. On being fertilized 
it germinates at once, and begins the development of the tiny 
plant known as the sporogonium, or plant of the second gener- 
ation, which produces spores able to germinate without fertili- 
zation. These plants, which always remain attached to the 
mother plant, have an extremely simple anatomical, as well as 
morphological, structure. In respect to the latter, there is, even 
in the highest forms, only an indication of a division into two 
organs, stem and capsule ; while in the lower forms not even 
the vestige of a stem is found, the egg-cell or spore devoting its 
entire energies to the production of spores. In the next higher 
class, the Musci, the corresponding plant of the second genera- 
tion reaches a higher development, though here it consists only 
of stem and capsule. 
