THE YAN YEAN RESERVOIR, VICTORIA. 53 
female gametangium in which the spore was lodged was of necessity much 
inflated, although the inflation was restricted to the exact place of lodgment. 
The conjugating-tubes were generally very wide and the zygospore projected 
into them, in some cases almost into the male gametangium. А few speci- 
mens were observed in which the zygospore was situated in the conjugating- 
tube midway between the two gametangia, and these examples afford further 
evidence of the identity of Zyynema Heydrichi, Schmidle, with Z. spontaneum. 
Schmidle’s specimens were from near Sydney, and the conjugation was 
lateral, the zygospores being formed in the conjugating-tube. The Victorian 
specimens exhibited no lateral conjugation, but aplanospores were formed in 
filaments which in other parts were conjugating in a scalariform manner. 
Family DESMIDIACEZE. 
Genus PENIUM, Bréb. 
12. РЕХШМ MARGARITACEUM, ( Ehrenb.) Breb. in Ralfs, Brit. Desm. (1848) 
p. 149, t. 25. figs. Lu-e; W.  G. S. West, Brit. Desin. 1. (1904) p. 83, t. 8. 
figs. 52-85. 
Var. IRREGULARE, W. & G. S. West, in Trans. Bot. Soe, Edin. xxiii. (1905) 
p. 14, t. 1. fig. 23. 
Long. 142 u ; lat. шах. 30 ш; lat. apic. circ. 20 p. 
Hab. Wallaby Creek Weir, at the outlet (July 1907). 
Genus PLEUROTÆNIUM, Nig. 
13. PLEUROTÆNIUM MAMILLATUM, G. S. West, in Victorian Naturalist, 
xxii. (1905) p. 70 ; in Journ. Bot, xliii. (1905) p. 252. 
P. submediocre, modice elongatum, cellulis diametro 14-17-plo longiori- 
bus ; semicellulee subeylindricæ, leviter et gradatim attenuate e medio apicem 
versus, inflatione subprominenti ad basin et marginibus 10-11-undulatis, 
undulis gradatim minoribus apicem versus; apicibus convexo-truncatis, 
verrucis magnis conico-mamillatis (subunguiculatis) subdivergentibus 6-7 
(visis 4) instructis ; membrana subsparse punctata. 
Long. 372-495 y ; lat. bas. semicell. 28-32 р ; lat. med. semicell. 27-314; 
lat. apie. semicell. sine verruc. 17-294, cum verruc. 21-25 и. (РІ. 3. 
figs. 1-2.) 
Hab. Yan Yean Reservoir, in the plankton (Feb.-Apr. 1905) and at the 
weedy margins (July 1905), but more frequent in the plankton. 
This species is readily distinguished by the large size and elongated 
character of the apical warts. The latter are mamillate in appearance, and 
possess a slight outward and upward curvature, which in some individuals is 
intensified until the warts become almost unguiculate. The total nmnber of 
