ZYGNEMACE, 85 
The English student may also consult with advantage a memoir “on 
the germination of the resting spores in Spirogyra,” by Dr. Pringsheim, 
translated in the Annals of Natural History, 2nd ser., Vol. xi. (1853), 
p. 210. “Onthe Structure and Division of the Vegetable Cell,” by J. 
M. Macfarlane, in Transactious of the Botanical Society of Edinburgh, 
Vol. xiv. (1881). Pringsheim’s Researches on Chlorophyll, translated by 
Professor Bayley Balfour, in Quarterly Journal of Microscopical 
Science, Vol. xxii., new series (1882). Darwin “On the Action of Car- 
bonate of Ammonia on Chlorophyll Bodies,” in Journal of the Linnean 
Society, Vol. xix. (1882). 
Section 1. Cells not replicate at the ends. 
A. Chlorophyll bands numerous (rarely two). 
Spirogyra crassa. Kutz. 
Sterile cells with the extremities truncate, equal or twice as 
long as broad. Chlorophyll bands four or more, making 1-12 
turns. 
Zygospores broadly and obtusely oval, membrane even. 
Sporiferous cells persistent, not swollen. 
Size. Cells -12--15 mm. diam. (Radh.), *15 mm. diam. 
(Petit), zygospore 14-15 diam, (Petit), -13 x °12; *14 x -12; 
16 x °12 mm. (1.C.C.). : 
Zygnema serratum, Hass. Alg. t. 18, f. 1. 
Spirogyra crassa, Kutz. Tab. v. t. 28, f.2; Kutz. Phy. Gen. 
t. 14, f.4; Kirsch. Alg. Schl. p.119; Petit Spirogyra p. 32, 
t. 12, f. 3, 4. 
Spirogyra Heeriana, Kutz. Tab. v. t. 28, f. 3. 
In ponds, &c. Fruiting in summer. 
Hassall says of his Z. serratum that the “filaments are of nearly the 
same diameter as those of Z. orbiculare, but less mucous, from which 
species it may readily be distinguished by the fewer number and ser- 
rated appearance of the spores, the larger size of the granules, and the 
form of the sporangia, which in Z. orbiculare are nearly spherical, and 
compressed, while in Z. serratum they are broadly ovate.” 
The sterile cells have a greater diameter than any other British 
species, whilst their length varies from about half a diameter to two 
diameters. The zygospore is comparatively broader than in S. jugalis, 
and slightly flattened, so that when seen in certain positions it appears 
to be narrower than it is, and more resembling that of S. jugalis. 
On plate 32, figs. 1 and 2, the nucleus is represented in the'centre of 
the cells. Pringsheim has recently remarked, as a fact hitherto unre- 
cognised, that “the threads of the protoplasm extending outwards from 
the central plasma mass in each cell, do not, as was supposed, end in the 
general protoplasmic lining of the cell wall, but each passes directly or 
by its branches to the internal surface of a chlorophyll] band, and there 
dilates in a trumpet-like manner, and grasps, as it were, an amylum 
body.”— Researches on Chlorophyll, p. 81. i 
Plate XXXII, fig. 1. a, sterile cells- X 200; 6, fertile cells with 
zygospores X 200; ¢, fertile cells of Rhynchonema form with zygo- 
spore X 200; d, outline of zygospore X 400. 
