This species has been under observation for four years and has been collected from ponds near Casey, Lerna, Coffeen and Donnellson, Illinois. The large, smooth spores, the reflexed conjugating cells, and the tube produced wholly by the male cells are the distinguishing characteristics. =S. hydrodictya= nov. sp. Cellulis vegetativis 75-100µ × 210-360µ, dissepimentis planis, chromatophoris 7-10, modo subrectis longitudinalibus, modo spiralibus anfractibus arctis .1-.5; cellulis fructiferis inflatis vel subinflatis; tubo conjugationis ex cellula mascula emisso; zygosporis lenticularibus vel globoso-lenticularibus, 80-120µ × 110-195µ, membrana media scrobiculis obsita, brunnea. Vegetative cells 75-100µ × 210-360µ, end walls plane, 7-10 chromatophores, either straight, or spiral making .1-.5 turns; fertile cells inflated or subinflated; conjugating tube formed by the male cell; zygospores lenticular or globose-lenticular 80-120µ × 110-195µ, median wall brown, pitted. Type in herb. E. N. T. Coll. No. 2661, 2665. Coffeen, Illinois. This is one of the most remarkable forms described in this genus. It combines large size, the lenticular spore form, and the habit of forming the conjugating tube entirely by the male cell. The conjugating tube has walls heavier than those of any known species. Conjugation is both lateral and scalariform, and occurs between scattered cells, very rarely continuous for 6-8 cells. In the fruiting condition the filaments form a mesh-work which suggests the specific name. It has thus far been found only in the Fath Pond, north of Coffeen, Illinois. =S. protecta= Wood. A study of American specimens of this species from Massachusetts, Connecticut, New Jersey, Michigan and Illinois, shows that like _S. Grevilleana_ there are always some cells with two chromatophores. I have twice found this species producing aplanospores. =S. tenuissima= (Hass.) Kütz var. =rugosa= Transeau. P. B.-A. specimen No. 456, Easton’s Pt., Newport, R. I., belongs to this variety rather than the type, as shown by the scrobiculate spore wall. In Mr. Bullard’s collection there are also specimens of the variety from Pennannock, N. J., and from Spy Pond, Lake St., Arlington, Mass. =S. Farlowii= nov. sp. Cellulis vegetativis 24-30µ × 70-180µ, dissepimentis replicatis; chromatophoris singulis, rarius duobus, anfractibus arctis 2.5-6; cellulis fructiferis inflatis (ad 39-60µ); zygosporis ellipticis, polis plus minus acuminatis, 32-45µ × 48-93µ, membrana media glabra, lutea. Vegetative cells 24-30µ × 70-180µ, end walls replicate; 1 (rarely 2) chromatophore making 2.5-6 turns; fertile cells inflated to 39-60µ; zygospores ellipsoid, ends more or less pointed, 32-45µ × 48-93µ, median wall smooth, yellow. Type in herb. E. N. T. Coll. No. 2955, 2956, 2957.