Vegetative cells 30-40µ × 120-300µ, with plane end wall; 1 chromatophore making 3-8 turns; fertile cells in groups of 2 or 4, inflated or enlarged and strongly reflexed; conjugating tube formed by the male cells; zygospores ellipsoid, 44-54µ × 90-150µ, median wall smooth, yellow-brown. Type in herb. E. N. T. Collection No. 2661, 2664, 2912.
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.
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.
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.