204 BOTANICAL GAZETTE (MARCH 
‘cell becomes larger and larger (fig. 27), and a small protuberance, 
which has a diameter equal to about half that of the conidiophore, is 
pushed out from the end (figs. 34, 41). There is now formed at the 
apex of this narrowed sterigma a swelling (jigs. 27, 35, 39, 42), which, 
after continued enlargement, finally receives the greater part of the 
protoplasm and all of the nuclear content from the basal portion. The 
process of cell-division, by means of which this apical conidium is cut 
off by a wall from the penultimate cell, will be described in some detail 
later, in connection with the description of cell-division in Empusa. 
Certain points should be noted here, however, and among them, that 
the term basidium, as applied to the penultimate cell, although in 
common use in this connection, should, in my opinion, be confined to 
the Basidiomycetes, where, morphologically, the true basidium is a 
very different spore-bearing structure from the penultimate cell bear- 
ing the conidium in Empusa. 
The penultimate cell forms the explosive mechanism by which 
the conidium is shot off. As the ring-formed wall which cuts through 
the base of the conidium travels progressively inward, the protoplasm 
passes through the narrowing opening leading from below, until at the 
close of abjunction, the basal cell retains only a thin parietal layer of 
protoplasm, but no nucleus. Continued swelling, due to the absorption 
of water, finally results in the bursting of the basal vesicle, thereby 
breaking the wall of the vesicle where it joins that of the conidium. 
In some forms, a ring-shaped scar is noticeable near the base of the 
conidium, marking the circle where the summit of the swollen basal 
vesicle was formerly attached. The septum which separates the 
conidium from the subterminal cell is at first usually pushed upward, 
thus resembling a columella (figs. 28, 30, 31, 36), but when the 
spore is shot off, this partition-wall reverses its former position, and 
in the conidium it appears as a prominent papilla (jigs. 29, 37, 43): 
When the basal vesicle bursts, its contents are thrown out of the open 
ruptured end and frequently persists as a slimy covering about the 
spore, serving in this case, perhaps, the double purpose of protection 
against excessive evaporation and of sticking the spore to the sub- 
stratum which it strikes. I have noted that the explosion, in the case 
of Empusa sciarae, sometimes throws the spore a distance of 67"; 
while BREFELD has recorded an even greater distance in the case of E. 
muscae, in which the spores are said to be sent as far as 2-3°™. 
