Cellulis vegetativis 28-33µ × 28-66µ; zygosporis incognitis; aplanosporis cylindricis vel tumido-cylindricis, 30-33µ × 24-58µ, sporangia complentibus; membrana media brunnea scrobiculata.
Vegetative cells 28-33µ × 28-66µ; zygospores unknown; aplanospores cylindric or tumid-cylindric, 30-33µ × 24-58µ, filling the sporangia, median wall brown, scrobiculate. Type in Herb. E. N. T. No. 1164, 1177.
This species is not uncommon in ponds, and pools throughout central Illinois. It was at first classified as aplanosporic material of Z. stellinum (Müller) Agardh. On going over the specimens in all my collections, however, it was found that in no case were the filaments containing the aplanospores connected with the filaments containing zygospores. This must be the final test of the identity of the species, as it occurs in some collections alone, sometimes associated only with fruiting Zygnema pectinatum, and sometimes with Z. stellinum.
Zygnema rhynchonema Hansg.
In a collection of algae made at the Minnesota Seaside Station, Vancouver Island, B. C., in 1901, by Professor Tilden, is a form which perhaps belongs here. The vegetative cells are from 22-28µ in diameter, and 32-52µ in length, while the European specimens are described as 16-20µ in diameter and 2-6 diameters long. The Vancouver specimens are producing both aplanospores (globose, 24-26µ in diam.), and zygospores (ovoid 24-28µ × 36-44µ) by the union of gametes through the partition wall separating the two gametangia. The specimens show some evidences of being in an abnormal condition.
SPIROGYRA Link.
S. Juergensii Kützing.
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.