162 



Mycologia 



as I have observed it, is similar to that Harper described in Pilo- 

 bolus. Furrows appear at the surface of the spore plasm and cut 

 inwardly to meet the clefts produced in the interior of the spore 

 plasm by vacuoles, which become angular (PL 16, fig. 8). The 

 spore plasm is thus cut up into irregular protoplasmic blocks con- 

 taining a variable number of very small nuclei (PI. 16, fig. 8). 

 Moreau does not describe or figure cleavage turrows in Circinella 

 conica. The irregular blocks are further divided by cleavage into 

 more or less oblong to sausage-shaped protoplasmic masses con- 

 taining four to five nuclei (PL 16, fig. 9). As in Pilobolus, these 

 blocks are transversely divided into roughly polygonal, one- to two- 

 nucleated protoplasmic masses. I agree with Moreau in calling 

 these protoplasmic segments the protospores. During the cleavage 

 process the protoplasmic mass undergoes shrinkage without ques- 

 tion, but I did not observe such a loose and open structure of the 

 dividing spore plasm as Moreau figures, and I am inclined to be- 

 lieve that his figure 28, plate 3, represents poor fixation and con- 

 siderable shrinkage. The protospores are, for' a time, connected 

 by delicate, gelatinous strands, which are probably an exudate of 

 the protoplasm (PL 16, fig. 10). The nuclei now divide and each 

 protoplasmic mass (protospore) swells and grows. The young 

 spores now become polyhedral and are closely pressed together 

 (PL 16, fig. 13). This expansion period is followed by a con- 

 traction; the multinucleated spores round up and form a cell-wall 



(pi. 16, % 14). 



The process of spore formation in Circinella minor may be sum- 

 marized as follows : 



1. Differentiation of spore and columella plasm. 



2. Formation of irregular multinucleate blocks of protoplasm by surface fur- 



rows and angular vacuoles. 



3. Further division by cleavage producing oblong protoplasmic masses contain- 



ing four to five nuclei (2 and 3 are contraction phases). 



4. Division of oblong to sausage-shaped blocks into one- to two-nucleated 



protospores. 



5. Protospores grow and become multinucleated (expansion phase). 



6. Spores round up (second contraction phase). 



7. Further contraction and formation of cell-walls. 



Harper has pointed out that in Sporodinia grandis there is an 

 abbreviation of the process of spore formation as compared with 



