166 BOTANICAL GAZETTE [SEPTEMBER 
detail of somewhat minor importance. The sexual differentiation 
on a single mycelium in the latter species may be perhaps a fore- 
runner of heterothallism, yet in each species the thallus as a whole 
is bisexual. 
Rather than attempt to restrict the terms monoecious and dioecious 
to either the gametophytic or sporophytic stage, it has seemed best 
for the purposes of general discussion in the present article to avoid 
the ambiguity of the expressions now in use by applying a separate 
set of terms to designate the sexual condition in the gametophyte 
and sporophyte respectively. Whether or not the precision thereby 
gained will compensate for the disadvantages of adding new words 
to an already overburdened vocabulary of technical expressions 
must rest with botanists whose interest in the subjects of sexuality 
embraces all the groups of the plant kingdom. 
Homothallic and heterothallic are terms already explained, which 
the writer has used to designate the species of the mucors charac- 
terized respectively by thalli sexually all alike, or by thalli sexually 
of two different kinds. Homothallic and heterothallic forms, there- 
fore, have bisexual and unisexual thalli respectively, and the terms. 
accordingly would correspond to the expressions monoecious and 
dioecious. Without changing the etymological significance, the mean- 
ing of the words homothallic and heterothallic may be appropriately 
extended to include a description of the degree of sexual differentia- 
tion in the prothallus or gametophyte of the archegoniates and 
spermatophytes, as well as in the thallus of the thallophytes. 
Homophytic and heterophytic are offered as equivalents in the 
sporophyte of the terms monoecious and dioecious. Although the 
“plant” in the common acceptation of the word is the sporophyte 
in the higher forms, the condition is reversed in the bryophytes. 
The words homophytic and heterophytic, therefore, as designations 
for the sporophyte are etymologically not above reproach, but will 
suffice in lieu of a more cumbersome combination. The terminology 
suggested has reference to the sexual differentiation as such. as 
accompanying morphological differences are to be considered a5 
secondary sexual characters and are not included in the classifica 
tion. 
It will now be possible to examine the sexual condition in the 
