176 BOTANICAL GAZETTE [SEPTEMBER 
term here is perhaps used in reference to the constant separation of 
the sexual organs on different shoots without regard to their ultimate 
connection on the protonema; yet the latter is as an essential part 
of the plant as the leafy axis, and if the species is in fact homothallic 
it is not to be called dioecious. Such forms as Funaria offer an 
interesting field for regeneration experiments to determine if pro- 
tonemata developed from antheridial and archegonial shoots differ 
at all in sexual character. 
Among the algae, Spirogyra, to mention a simple example, is a 
familiar genus in which homothallic species are known to occur, 
and in which heterothallism is strongly to be suspected for certain 
species from a mere morphological investigation. In fig. 7, which is 
taken from STRASBURGER’S textbook, is represented Spirogyra longata. 
It seems in this type to be 4 
matter of indifference whether 
the two conjugating cells come 
from the same or from different 
filaments are bisexual and the 
species is therefore homothallic. 
In Debarya, represented in fig: 2» 
the zygospores are formed, as 10 
the heterothallic mucors, midway 
between the two thalli, between 
which no differences are apparent: 
In the most common form ° 
conjugation, however, which is represented in fig. 3, one filament 
seems to be receptive, since it contains all the zygotes formed be- 
tween two conjugating filaments and has therefore been considered 
female. Though rather improbable, it is yet imaginable that a fila- 
ment which acts as female toward one thread might function %* 
male toward another. Theoretically it would not be a difficult task 
to determine by cultivation the sexual character of any form je 
producing zygospores. 
Fic. 1 Fic, 2 Fic. 3 
Spirogyra Debarya Spirogyra 
The Saprolegniaceae form sexually one of the most interesting - 
groups among the fungi. In Achlya racemosa the i 
branches are borne from the stalk of the oogonium, in A. polya 
threads. Obviously here the 
