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SPIROGYRA 151
3. Spirogyra juercensii Kiitzing 1845. Phycologia Germanica,
p. 222.
Vegetative cells 24-30 /a x 60-125 /a, with plane end walls; i chromatophore,
making 2 to 4 turns; conjugation scalariform and lateral;
tubes formed by both gametangia; fertile cells cylindric or enlarged
toward the middle (to 34^); zygospores and aplanospores eUipsoid,
28-33 M X 50~75^-; median spore wall yellow, smooth. (PI. I, Fig. i;
PI. XXI, Fig. 3.)
United States: California; from Wisconsin, Iowa, and Texas to the
east coast.
Widely distributed in Europe; South America; Australia.
Distinguished from S. longata by the ellipsoid spores. Sometimes at
maturity the stretching of the fertile cell wall shortens that end of the conjugating
tube, and the tube has the appearance of having been formed by
the male cell as in S. punctijormis and S. micropunctata. From the former
it is distinguished by the ellipsoid, smooth spores; from the latter by the
smaller size and smooth spore wall. In a collection from Mississippi cylin-
drically inflated akinetes with thick walls were present together with zygo-
spores. The dimensions of the akinetes varied from 48-60 ju x 108-140 /.i.
(PI. I, Fig. I.)
4. Spirogyra singularis Nordstedt 1880. Bot. Notiser 1880.
p. 118. Wittrock and Nordstedt Algae Exsiccatae, No. 361.
Vegetative cells 29-39^1 x 60-240 /x, with plane end walls; i chromatophore,
making 3 to 7 turns; conjugation scalariform; tubes formed
by both gametangia, fertile cells cylindric, rarely enlarged; zygospores
elHpsoid, 27-36 jn x 46-70 jU,; median spore wall yellow, smooth. (PI. XXI,
Fig- 4-)
United States: Michigan and Texas, to the east coast.
Described from New Zealand; reported from Finland; South Africa;
China; Brazil.
Distinguished from S. longata by the ellipsoid spores. In all specimens
seen the chromatophores were narrow and the spirals very open.
5. Spirogyra silvicola Britton 1943. Amer. Jour. Bot. 30, p. 799,
Fig. I.
Vegetative cells 32-42 m x 63-267 ju., with plane end walls; i chro-
matophore, making 1.5 to 3 turns in the cell; conjugation scalariform;
tubes formed by both gametangia; receptive gametangia cylindric or
slightly enlarged; zygospores ellipsoid to cylindric-ovoid, 36-43 /a x
56-103 /a; all walls smooth; median wall yellow or brown at maturity.
(PL XXI, Fig. 7.)
United States: Illinois, Somme Forest, Cook County, May 15, 1938
(Britton Coll.); Texas, Austin (Taft Coll.).
Vegetative cells similar to those of S. singularis; zygospores much larger.