


1901] CURRENT LITERATURE 215 
Isoetes lack this coat. All of these membranes grow by intussusception, and 
the author lays stress on the fact that the perispore and exospore are of 
quite different chemical nature, and yet are both growing simultaneously by 
intussusception. Finally, between the mesospore and the protoplasm con- 
tent appears a thin film of cellulose, the endospore. The nourishment 
needed for the growth of these membranes is derived from the sporangium 
wall and trabeculae, not from the tapetal cells. Until the walls are formed 
the spore content is relatively very small. 
The author was less successful in his work in Selaginella. Owing to the 
smallness of the megaspore and to imperfect technique (he never succeeded 
in avoiding shrinkage) he failed, like all his predecessors, to make out the 
stages of the development of the megaspore. The megaspore mother cell is 
easily recognized, but how it divides into spores is not known. 
Heinsen’s account and Fitting’s disagree in almost every particular as 
regards the interpretation of the spore contents and the origin of the several 
coats. The “nucleus” (according to Heinsen) is the entire protoplasmic 
content. Heinsen’s “nucleolus” Fitting interprets as the nucleus. The 
several small “corpuscles,” whose nature Heinsen could not explain, are, 
according to this author, the nucleoli. The sequence of events as regards 
the development of the coats is much like that of Isoetes, making an addi- 
tional reason why [soetes and Selaginella should not be separated in any 
system of classification. The author thinks that the extremely smal] amount 
of protoplasm in the spore can have nothing to do with the nourishment of 
the spore coats, which soon far exceed it in thickness and bulk. Between 
the tapetum and the four megaspores is a sort of slimy matter which Bower 
interpreted as the remains of the disorganized sterile mother cells. Fitting 
Says that these cells do not disorganize, and that the slime is a secretion from 
the tapetum, which acts like a gland. This material nourishes the spores up 
to their maturity, when they fill the entire sporangial cavity. Like those of 
Isoetes, the spore walls develop by intussusception. A very significant fact 
is that the greatest growth of the spore walls takes place when they are not 
in contact with the plasma body within. Four walls are found, exospore, 
mesospore, endospore, and perispore (the latter sometimes lacking in certain 
species). The increase in size of the plasma body without corresponding 
increase in the amount of matter of which it consists, followed by cell divi- 
sion and the formation of the prothallium, were not followed in detail. The 
author says, however, that in some species this occurs before the spores are 
shed (S. Martensii, S. Galeottiz), and in others ‘a long time afterward,”’— 
FLORENCE May Lyon. 
