The specimen in P. B.-A. No. 510 from Knightsville, R. I., distributed under the name of _S. longata_ (Vauch) Kütz. with cell diameter 27-30µ, and ellipsoid spores 30-33µ in diameter, fertile cells enlarged, evidently belongs to this species. The spores of _S. longata_ are distinctly ovoid with rounded ends. In the Illinois specimens the spores of _S. Juergensii_ frequently occur with diameters up to 33µ. =S. varians= (Hass.) Kütz. The varieties _scrobiculata_ Stockman and _minor_ Teodoresco have not been reported from America. They both occur rarely in Illinois. The latter I have also seen in material collected by Mr. Charles Bullard, at Lynnfield, Mass. The former is characterized by its scrobiculate spores, the latter by its smaller dimensions throughout. In my herbarium _S. varians scrobiculata_ is represented in Collections No. 1799, and 1881; and _S. varians minor_ in Collection No. 2951. =S. Borgeana= nov. sp. Cellulis vegetativis 30-35µ × 50-200µ, dissepimentis planis, chromatophoris singulis anfractibus arctis 1.5-5; cellulis fractiferis altero latere inflatis, altero latere (in quo conjugatio sequitur) rectis; zygosporis ellipticis, 33-40µ × 54-70µ, membrana media flava, glabra. Vegetative cells 30-35µ × 50-200µ, end walls plane, 1 chromatophore making 1.5-5 turns; fertile cells inflated on the outer side, straight on the conjugating side; zygospores ellipsoid 33-40µ × 54-70µ, median wall yellow, smooth. Type in herb. E. N. T. Coll. No. 1883, 1890. Charleston, Illinois. This species bears some resemblance to a form of _S. varians_ figured by Professor Borge.[D] It differs from his figure in that the conjugating side of the fertile cells is not at all swollen, and the dimensions are somewhat larger. If this form had been found but once it would have been passed over as a variation intermediate between _S. Juergensii_ and _S. varians_. But it has been found several successive years in a small stream south, and at a small pond west of Charleston, Illinois. =S. lutetiana= Petit. So far as I am aware no specimens of this species have been found in America. The Illinois record in my list[E] is an error. The P. B.-A. specimen labelled _S. lutetiana_ is _S. fallax_ (Hansg.) Wille, as shown by its often replicate cell walls, verrucose spores and the number of chromotophores. =S. velata= Nordstedt var. =occidentalis= Transeau. Specimens of this variety have been distributed in the P. B.-A. No. 96, under the name of _S. dubia_ Kütz. var. _longiarticulata_ Kütz. from Oak Bay, Victoria, British Columbia (N. L. Gardner). The spores are for the most part not mature but they show the characteristic scrobiculate markings of the median wall. =S. Lagerheimii= Wittrock.