Cushman: Zygospores of desmids 225 



face. This condition is more like the third case mentioned under 

 Closteriiun Dianae^ but there the semicells do not adhere in the 

 peculiar manner of this species. Wolle does not show this char- 

 acter in either of his figures of fruiting specimens of this species. 

 All the specimens seen had this character. 



The second character is the variation in the production of 

 either single or twin zygospores, the latter condition being much 

 the more frequent. With the exception of the above characters 

 the stages are comparable to those seen in the preceding species. 

 Fruiting specimens of this species w^vt also abundant in the col- 

 lection from Reading. 



Diameter of completed zygospore, 78 /i. 



M 



FIGURES 



The zygospore of this species was figured in Ralf's British 

 Desmids, and that I believe is the only original figure of the species 

 in its fruiting condition. The zygospore is large with fairly large 

 and stout spines, many of them bifurcate at the tip. Just before 

 the spore is fully formed there Is a gelatinous covering which ex- 

 tends partway out upon the spines. This disappears as the zygo- 

 spore reaches completion, entering probably into the formation of 

 the covering. The form of the zygospore is not exactly spherical, 

 but slightly elongated. 



* 



Lat. zyg. s. sp. 75 ,w ; c sp. 95 /^ ; long. zyg. s. sp. 75 /^ ; c. 



sp, 103-105 /i. 



Common in the material from Reading. 



Penium Clevei crassum W. & G. S. West. Plate 7, figure 8. 



This variety was found to be common in the material from 

 Pondville, making the first record for it in America. The zygo- 

 spore both of the typical form and of the variety has hitherto been 

 unknown. It is spherical with numerous, broad, squarely trun- 

 cated spines as in the figure. The cells in the figure have not the 

 roughened apices which, however, they do possess in the specimens. 



Long. cell. 80-84 /i, lat 40-44 /-^ : diam. zyg. c. proc. 6^-2^ fi, 

 s. proc. 54-57/^. 



Cosmarium pseudoorbiculatum sp. nov. Plate 7, figure 9, 



This species has been confused with C. ofhiciilatiim Ralfs. It 

 is evidently the same as that figured and described by Delponte 



