461 
Zygospores of Sporodinia grandis. 
hyphae or sexual branches. In some cases, one branch appears slightly 
smaller than the other, but this seems to be the result of physiological 
rather than morphological conditions. The protoplasm flows out into the 
ends, gradually growing denser until the ends of the hyphae are densely 
filled, while the regions further back are vacuolated. These observations 
can easily be made in fresh material. 
When the internal structure of the branches is studied, however, there is 
found to be a slight variation in the activity of the sexual branches. Leger 
describes two types of branches : in one, the protoplasm fills both of the 
sexual branches ; in the other, the protoplasm is retracted from the wall. 
According to my studies, this appears to be due to a difference in age. In 
the earlier stages the protoplasm fills the branches, but later a retraction 
of the protoplasmic mass occurs (PI. XXXV, Fig. 3). This retraction is 
usually restricted to one branch, but occasionally both show it to some extent. 
Even in the latter case, however, the retraction is more marked in one 
branch than in the other. The writer, contrary to the results obtained by 
Miss McCormick, has been unable to distinguish any marked differential 
staining between the two protoplasts of the two sexual branches. A granular 
substance usually fills the intervening space where the protoplasm has 
drawn back from the wall. This was particularly evident in preparations 
stained with iron-haematoxylin and Bismarck brown, for in such preparations 
the granular substance always stains brown. This is probably the substance, 
described by Vuillemin ( 33 , 34 ), which forms the secondary membrane before 
resorption occurs. 
Many nuclei are found distributed in the protoplasm of the young 
sexual branches. Nuclear divisions were not observed, but there seems 
little doubt that they occur about this time, because there is a marked 
increase in the number of nuclei, which cannot well be explained on the 
basis of subsequent migrations. The nuclei are extremely small (PI. XXXV, 
Fig. 1 a). The main part of the nucleus is granular in appearance, and 
stains violet or slightly red in Flemming’s triple stain. The central part 
of the nucleus stains a brilliant red, and appears to be a constant organized 
structure. It is very similar in appearance to the nucleoli of the nuclei 
of the higher forms, but the fact that this structure is constant through all 
the stages of development would suggest that it is chromatin in nature 
rather than that it is a nucleolus. The true nature of this material will 
remain a question, however, until nuclear divisions have been observed. 
Lendner describes the nuclei as being formed of two small masses closely 
associated, which divide simultaneously and give the double division 
described by Maire in the Basidiomycetes. The writer, however, has 
made a careful study of the nuclei in the germinating spores where 
division must occur, but has been unable to find any variation from that 
described above. 
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