1918] FITZPATRICK—RHIZINA 211 
which remain behind lie at this stage in a rather restricted zone 
at the periphery. 
This pronounced vacuolation and thinning of the cytoplasm of 
the ascogonial cells renders less difficult the study of the nuclei, 
and at this stage, in the writer’s preparations, they seem always 
to lie in pairs. At no other stage in the development of the archi- 
carp, either before or after the formation of pores in the transverse 
septa, have paired nuclei been found in any of the cells of this struc- 
ture. This, however, may be due in large measure to the fact that 
the dense nature of the cytoplasm and the crowding of the nuclei 
render the determination of this point extremely difficult. _ 
The presence of paired nuclei in any of the cells of the archicarp 
is a matter of the greatest interest and importance. This is espe- 
cially true since an antheridium is absent. The determination of 
the origin of the two nuclei which constitute a pair, however, is 
fraught with considerable difficulty. It is evident that.they are 
either potential sex nuclei which have had their respective origins 
in the same or different cells of the archicarp, or sister nuclei which 
have resulted from a recent more or less simultaneous division of 
the archicarp nuclei. If they are sex nuclei, it is to be expected - 
that they will either fuse in the archicarp or migrate side by side 
into the ascogenous hyphae, where they will undergo conjugate 
divisions preceding the fusion in the ascus. 
Fusion of these pairs of nuclei in the cells of the archicarp has 
not been observed. Although occasionally the two nuclei lie in 
actual contact, fusion stages have not been found. Moreover, no 
nuclei of larger size have been seen which might from analogy be 
assumed to be fusion nuclei. A thorough examination of the nuclei 
in the ascogenous hyphae has failed, moreover, to demonstrate 
conjugate divisions. In some instances groups of nuclei in fours 
have been found lying in such a position as to suggest their origin 
from conjugate divisions, but these cases are not numerous enough 
to carry conviction. No mitotic figures, either of simple or con- 
jugate division, have been seen in these hyphae, nor in any of the 
cells of the archicarp. The writer has attributed their absence 
to the fact that all of his material was placed in the fixing solution 
at one time. Periodicity of mitosis thus could easily explain their 
