Nov., 1915] Notes on the Zygnemales 21 



ZYGNEMA Agardh. 



Z. pectinatum (Vauch.) Agardh. 



This is probably common in the eastern half of the United 

 States at least. In Illinois along with the type occurs the 

 variety conspicuiim (Hass.) Kirchner, and a variety with large 

 spores. This latter variety in fact is more common than the 

 type. 



var. crassum nov. var. Cellulis vegetativis 30-40/i x 20-80/^; 

 zygosporis 40-55/i x 50-60^l, ceterum ut in typo. 



Vegetative cells 30-40/x x 20-S0)u; zygospores 40-55/x x 50-60/x, 

 otherwise like the type. Type in herb. E. N. T. Collections 

 No. 2350, 2392, 2660, 2685. 



Z. ericetorum (Kiitz) Hansgirg. 



Professor G. S. West has studied the reproduction of this 

 species and finds that it is a true Zygnema and that the descrip- 

 tion and figure by De Bary, which shows the cutting off of two 

 special gametangia before the union of the gametes is at fault, 

 consequently there is no longer any need of maintaining the 

 genus Zygogoniiim Kiitzing. 



Z. peliosporum Wittrock. 



Specimens of this species have been distributed under the 

 name of Z. chalybeosperniim Hansgirg, in P. B.-A. No. 808 

 from Boswell, Calif. (N. L. Gardner) ; Amer. Alg. No. 156 from 

 Ft. Collins, Colo. (J. H. Cowan); and Amer. Alg. No. 392 

 from Vancouver, B. C. (J. E. Tilden). Z. chalybeospermum 

 has the median wall smooth, but the spores of all of the above 

 specimens have distinctly scrobiculate median walls. In size 

 the specimens show a somewhat greater variation in dimensions 

 than has been recorded for European localities. 



Z. cruciatum (Vauch) Agardh. 



Specimens of this species have been found at Path Pond, 

 north of Coffeen, 111., in which both zygospores and aplanospores 

 occurred in abundance. The aplanospores fill or slightly 

 enlarge the vegetative' cells as in Z. CoUinsianuni Transeau,* 

 but the ends of the spores are usually more nearly truncate, 

 34-50m X 30-80At. At Casey, 111., a variety with the same 

 dimensions but steel blue spores occurs in the old Ice Plant 

 Pond. 



*See Fig. 3, Plate XXV, Amer. Jour. Bot. 1:301. 1914. 



