164 BOTANICAL GAZETTE [SEPTEMBER 
Figs. 1-5 were taken from test tube material and illustrate stages 
in conjugation. The progametes, as also the gametes, are fre- 
quently unequal, but this fact, as in the case of Rhizopus (/. ¢. 269), 
is probably associated merely with an inequality in the amount of 
nutriment received from the opposite zygophoric hyphae and has no 
sexual significance. The zygospores vary in size from 46X4op to 
80X63H, and average about 7058, with the longest diameter at 
right angles to the suspensors. The mature zygospore (jig. 4) is 
nearly opaque and thickly beset with comparatively long spines, 
which frequently, however, seem to be more or less arrested in their 
development, so that individual zygospores taken from the same cul 
ture may present a considerable difference in appearance. In Van 
Tieghem cells, where the amount of nutrient is necessarily scant, 
conjugation has not been directly followed under the microscope. 
In test tube cultures zygospores form chiefly in the lower parts of the 
tube below the conidial fructifications, producing a reddish-brown 
mass of minute specks which singly are hardly noticeable without 
the aid of a hand lens. Hyphae from which progametes are devel- 
oped do not as a rule take part in conidial formation, yet by 4 ae 
ful search one may find instances showing the two forms of fructif- 
cation in direct connection with the same hypha (fig. 3): Whether 
or not the zygophoric hyphae are mutually attractive, as is the cas 
with many forms, has not been determined. The contact, howevé 
of sexually opposite hyphae seems to be a stimulus to-an increas 
branching, for in the region of zygospore formation the conjugatn? 
hyphae are much branched and closely entangled. A scalariform 
arrangement of the zygospores is common, and progametes pes 
occasionally form so close together on two adjacent filaments a5 . 
give rise to twin zygospores (fig. 5) supported apparently by fork 
suspensors. Instances have also been observed in which oné side 
alone shows an apparent forking of the suspensor, and in other orl 
cases the suspensor of one zygospore has the appearance of a sim 
branch from that of another. The usual condition is that % : 
(figs. 1-4), where the progametes are developed laterally from adj 
cent hyphae at their points of contact. One zygophoric hypha ss 
be laterally met by the termination of the other, but it 1s cert 
seldom the case that their contact is exactly terminal. 
