1906) OLIVE-—DEVELOPMENT OF EMPUSA 201 
cells which make up the hyphal filaments. These branches appear 
to be put forth more or less simultaneously, in this species but one from 
each cell. The cell swells up and becomes rounded off somewhat at 
its ends (fig. 13). One or more vacuoles appear in the protoplasm 
and a protuberance is pushed out from one end of the cell; this grows 
into the radial hypha destined to become the branched conidiophore 
(figs. 12, 14,15). The two forces, the swelling and consequent round- 
ing off of the cells at the ends and the pushing out of the branch, com- 
bine to split the partition-walls between the cells, thus causing the 
hyphae to become easily broken up into one-celled segments, the 
“hyphal bodies” of THAXTER (figs. 1, 12). I have seen similar 
hyphal segments, forming in these instances also the origin of the 
radial conidiophores, as well in my preparations of E. culicis and FE. 
americana; but other species promise interesting variations from this 
common type of pre-reproductive development. In Empusa sp. 
and E. aphidis, for example, the vegetative hyphae remain, up to the 
very initiation of the reproductive stage, either unicellular, or at least 
with cross-partitions at only rare intervals. In such instances, there- 
fore, no breaking up into “hyphal bodies” occurs; but the vegetative 
hyphae appear to grow out directly into the conidiophores. 
As BREFELD and THAXTER have pointed out, the first hyphae to 
appear in the external growth of the fungus form the rhizoids, by 
means of which the host is fastened firmly to the substratum. In the 
common house-fly, the host is attached by means of its proboscis. . In 
E. sphaeros perma, according to BREFELD, bundles of rhizoids break 
out more or less irregularly from the under side of the body of the 
insect and attach it to the substratum. According to THAXTER, 
these rhizoidal hyphae may branch, and may terminate in a kind of 
expanded sucker, which apparently secretes a viscous substance. . 
In Empusa sciarae, rhizoids are developed more or less abund- 
antly from the under side of the abdomen of the fly, or, in the case of 
the larva, from almost any point on the under side of the body. In 
certain forms of E. aphidis, groups of rhizoids break out from the 
under surface of the insect and form large sucker-like hold-fasts. In 
several instances, I have counted three of these hold-fasts from aphides 
parasitic on Solidago. Fig. 10 shows one of these sucker-like bundles 
of rhizoids in section; and fig. rz a highly magnified hypha from near 
