228 CusHMAN : Zygospores of desmids 



Figure 15 shows an early stage In the formation 2Xi^ figure 16 



the completed zygospore. 



Lat. cell. 5 5-62 /i, lat. zyg. s. sp. 59//, c. sp. 84//. 



This variety was much more frequently found than the typical 

 species in the material collected by Mr. Fisher at Reading, Mass, 



+ 



Staurastrum polytrichtim readingense var. nov. Plate 8, fig- 

 ures 18, 18^. 



This variety differs from the typical form in being more densely 

 set with smaller and shorter spines. In other characters it is much 



r 



the same. 



The fruiting condition oi this species has, 1 believe, not been 

 figured. The zygospore of this variety is a peculiar one. It is in 

 the main spherical and is thickly set with spines having a broad 

 base and a trifid apex each portion of which is bifurcated. The 

 whole zygospore including the spines is thickly set with large 

 elongated granules giving a peculiar appearance, especially to the 

 spines. The detail of a single spine showing this condition is 

 given \n figure i8a, 



Lat. cell. 52/i, lat. isthm. 16 (j.: lat. zyg, s. sp; 53/^, lat zyg. 



c. sp. 78 /i. 



Found at Reading, Mass. 



Staurastrum eustephanum (Ehrenb.) Ralfs. Plate 8, figures 

 19, iga. 



The zygospore of this species has, I think, never been figured. 

 It is spherical in form with many processes, fairly wide at base, 

 but on the whole slender. Near the top it divides into three 

 branches, each one of which is again divided and the tips of the 

 divisions bifurcate. 



Lat zyg, s. proc. 45 //, c. proc. 84 /a 



Found both at Pondville and at Reading, Mass. 



Wolle figures three distinct forms of this species. One of 

 these (//. 5p, figs. ^S) is smaller than the typical form with 

 "spreading swallowtail-like ends of processes." This may be 



called van minnesotense 7wdis. He also figures another variety 



(//. 59, fig' ii\ with elongated processes. This variety may be 



called var. Wolleanum nobis. 



Boston Society of Natural History. 



