1906] OLIVE—NUCLEAR AND CELL DIVISION OF EMPUSA 245 
In these preparations, however, the thin, delicate walls are not at all 
easy to differentiate. I am convinced that, unlike the cases just re- 
ferred to, in Empusa a delicate wall grows simultaneously with the 
cleavage-furrow and not later. The figures which show abstriction 
of the conidia furnish sufficient evidence for this conclusion. In this 
case, the process of abstriction takes place essentially like the cell- 
division described for conidiophores, except that here the cleavage- 
furrow grows through a mass of cytoplasm instead of through a cen- 
tral vacuolar space. In jig. 38, the completed wall separating the 
conidium from the basal cell of the conidiophore may be plainly 
seen, since the protoplasm is shrunken away on both sides. But in figs. 
28, 30, 31, 36, although the cleft itself at the base of the conidium is 
brought out with diagrammatic clearness, the wall which accompanies 
it is not so evident. Two reasons may be noted here, however, 
which are not so apparent in the case of conidiophores, for the con- 
viction that the partition-wall is also present in these instances. The 
wall which cuts off the conidium, when completed, as was noted 
above in the case of the newly formed septa in conidiophores, is forced 
upward by the greater turgor of the basal cell, and here forms a kind 
of columella within the conidium. While it is possible that the 
cleavage-furrow itself might be stretched and forced upward in this 
fashion, yet it is more than likely that the unsupported plasma-mem- 
branes bounding the cleft could not withstand the considerable 
pressure which is developed. A further reason for the belief in the 
necessity of the cooperation of a ring-formed wall in these instances 
is seen in the shooting off of the conidia immediately on the comple- 
tion of their abjunction. In figs. 29, 37, 43, are shown conidio- 
spores which have evidently just been shot off and in which the tur- 
gescence of the protoplasm has now reversed the position of the cross- 
wall, making a papilla at the base instead of an indentation. We 
see clearly in jig. 37 the delicate wall shrunken away from the spore- 
plasm. An uncompleted wall at the time of the discharge of the 
conidium would evidently allow the escape of the protoplasmic 
contents. . | 
GENERAL DISCUSSION. 
_ It is clear that the division of the nuclei of Empusa which has 
just been described, although apparently resembling in some respects 
