ZYGNEMACE^E. 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. "On the Structure and Division of the Vegetable Cell," by J. 

 M. Macfarlane, in Transactions 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 hands 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 -I-li 

 turns. 



Zygospores broadly and obtusely oval, membrane even. 



Sporiferous cells persistent, not swollen. 



SIZE. Cells -12--15 mm. diarn. (Rahh.), '15 mm. diam. 

 (Petit), zygospore -14--15 diam. (Petit), '13 x '12 ; -14 x '12 ; 

 16 x '12 mm. (M.C.C.). 



Zyguema 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, 

 1. 12, f.-3, 4. 



Spirogyra Heeriana, Kutz. Tab. v. t. 28, f. 3. 



In ponds, &c. Fruiting in summer. 



Hassall says of his Z. serratvm 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. orbicidare are nearly sphserical, 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. 



Plate XXXII. fig. 1. a, sterile cells X 200 ; b, fertile cells with 

 zygospores X 200 ; c, fertile cells of Bhynchonema form with zygo- 

 spore X 200 ; d, outline of zygospore X 400. 



