3o8 American Quarterly Microscopical Journal. 



E. oblongum, Rlfs. Cells 0.125 — 0.14 long, verrucose. Halves five 

 lipped; terminal lips with narrow opening. 



E. didelta, Rlfs. Cells about 0.125 1. Halves three-cornered, five 

 lipped. Lips round or wavy. 



E. Ralfsii, Rb. Cells 0.035 1- ! three-cornered and three-lipped. 



E. verrucosum, Ehr. Cells 0.06^0.1 1., warty ; halves with three- 

 heart-shaped lips of equal size. 



E. hinale, Rlfs. Cells 0.022 1. Halves distinctly three-lipped, 

 almost quadratic ; terminal lips emarginate, with corners 

 pointed. 



10. (ien. Cosinariui/i, Corda. Cells elliptic, deeply constricted in 



the middle ; chlorophyll (in cross section) radial, with a 

 central starch granule. Zygospores warty or radiate. 

 Numerous ill-defined species, some very common. 



C. Botrytis, Mgh. Cells 0.033 — 0.05 1., densely verrucose or 

 spinous, nearly as broad as long, rounded or blunted. Very 

 changeable in form and appearance. 



C. quadratum, Rlfs. Cells up to 0.055 1-' smooth, almost quadra- 

 tic, corners rounded. 



C. cucumis, Corda. Cells 0.06 — 0.08, smooth ; halves cylindrical 

 or almost spherical. 



C. Phaseolus, Breb. Cells 0.025 — 0.03, smooth, circular; halves 

 turgid in the middle. 



C. Cucurbita, Breb. Cells large as 0.02 1., less constricted in the 

 middle; halves egg shaped. 



11. (ren. Arthrodesmus, Ehr. Cells deeply constricted ; halves 

 laterally prolonged into spinous projections. Zygospores 

 spinous. 



A. convergens, Ehr. Halves elliptic, with simple, converging 



spines. 

 A. octocornis, Ehr. Halves with four simple spines or projections. 



12. Cien. Xanthidium, Rlfs. Cells spherical, deeply constricted, 



provided with spines. Zygospores spinous. 



X. aculeatuin, Ehr. With simple awl-like spines, and scattered 

 warts. 



X. fascicuiafu/n, Ehr. Halves kidnej-shaped, or obtusely eight- 

 cornered, the outer corners each with two spines, otherwise 

 smooth. 



X. anfilopceum, Ktz. Halves obtusely six-cornered, ends broad, 

 somewhat wavy, each of the four outer corners with a ])air of 

 bent spines. 



