48 DR. G. S. WEST ON THE ALGÆ OF 
Crass. cell. veget. 8-10 u; long. spor. 18-36 ш; lat. spor. 10-12 д. 
Hab. Yan Yean Reservoir: sparingly among Mougeotia victoriensis and 
several species of Oedogoniim at the weedy margins (Nov. 1905). Also more 
abundantly, mixed with Yribonema bombyeina, in small, shallow pools in 
Honeysuckle Flat (Sept. 1907). 
This species of Ulothriv is at once characterized by the peculiar nature of 
its spores. They arise, either singly or in chains of upwards of 20, from the 
ordinary vegetative cells. During the formation of a spore the vegetative 
cell increases to about twice its volume and becomes ellipsoid or doliform. 
The cell-wall increases much in thickness and possesses in the ripe spore 
numerous coarse scrobiculations. It is the scrobiculated character of the 
wall of these spores which distinguishes U. idiospora from all other described 
species of Ulothriv, The spores are resting-spores (hypnospores) and come 
under the heading of **akinetes,? as they arise by the further growth of the 
original mother-cell, and not by the formation of an entirely new cell-wall 
within that of the mother-cell. 
In the thickness of its vegetative filaments U. idiospora is very similar to 
U. tenerrima, Kütz. (vide Hazen in Bull. Torr. Bot. Club, xi. (1902) p. 151, 
t. 21. figs. 5—1), but the cells are generally proportionately longer. The 
akinetes of U. tenerrima, and indeed of all the allied species, are shorter and 
more angular than those of U. idiospora, with thinner, perfectly smooth 
walls. 
Spores were rarely observed in the filaments from the weedy margins of 
the reservoir, but from the shallow pools in Honeysuckle Flat most of the 
filaments were in a state of spore-formation. Мг. Hardy writes that the 
water of these pools was warmed by the sun almost to a tepid condition, as 
they were only about four feet across and but a few inches deep, having been 
left by the receding of the water of the reservoir. Spore-formation seems 
thus to have been produced by the increase in temperature of the water and 
the incipient drying-up of the pools. — The spores would remain in the mud 
on the pools becoming quite dry, germination taking place on. the re-flooding 
of these hollows, which takes place when the water of the reservoir is very 
high. 
Genus RADIOFILU М, Schinidle. 
6. RADIOFILUM CoNJUNCTIVUM, Schmidle, in Flora, Bd. 78 (1894), p. 47, 
t. 7. figs. 4-5 : Chodut, “ Algues Vertes de la Suisse," Beitr. Kryptoqameull. 
Schweiz, 1902, р. 271.—R. apiculatum, W. у G. 5. West, in Journ. Bot. 
xxxiii. (1895) p. 52; Bohlin, in ВИ. till К. Se. Vet- Akad. Handl. xxiii. 
(1897) p. 10, t. 1. figs. 6—8. 
Lat. cell. 45-6 y ; long. cell. 5-8 м. (РІ. 6. figs. 1-3.) 
