i57 
Thraustotheca , a Peculiar Water-Mould . 
isolated by the careful manipulation of a delicate platinum needle, and 
transferred to nutrient agar. This method proved more simple than the 
floating cover-glass method of Trow (29), Kasanowsky (16), and others, and 
quite as efficient. After pure cultures from single zoospores had been thus 
secured, stock cultures were maintained in flasks on fairly dry cornmeal 
mush, a medium in which the mycelia retained their vitality especially well. 
An abundance of material in the several stages desired for study was 
secured by the methods of Klebs (18) and his successors, by growing 
mycelia in a variety of favourable liquid media and transferring them to 
sterile water or various solutions in which the development of the fungus 
was followed. Beef extract (i to 3 per cent.), diluted beef juice, and 
filtered decoctions of split peas, yellow cornmeal, seed sweet corn, oatmeal, 
or other cereals were used. To suitable amounts of the medium in Petri 
dishes several bits of mycelium on agar were transferred; and after three 
to five days at laboratory temperature the resulting mats of mycelium 
were of sufficient size for use. 
Development oe the Fungus. 
In its development under normal conditions Thraustotheca clavata 
follows a regular cycle, since the mycelium gives rise first to sporangia and 
later to sexual organs. For convenience, therefore, the successive stages 
will be considered in the order of their appearance.- 
Mycelium. In both pure and gross cultures the mycelium consists of 
a number of main hyphae which grow out in a radial direction, and by 
branching and rebranching give rise to a thick mat of interwoven filaments. 
Certain variations in size, shape, structure, and method of branching 
characterize the hyphae in different nutrient solutions ; but since these 
variations have already been described by Klebs (18), Kauffman (17), 
Horn (14), and Obel (22), for several Saprolegniaceous species, they need 
not be discussed here. 
In pure cultures the hyphae frequently contain masses of pectin which 
vary in extent from knobs or bosses on the inner wall surface, and from 
discoid or cylindric septa (PI. IV, Fig. 37 ) to lobed structures occupying 
a large part of the lumen. Frequently also portions of the hyphal content 
may separate, become surrounded by a delicate wall, and then resume 
growth to form endogenous hyphae, which often grow in opposition to 
each other until one or both may be forced out through the original hyphal 
wall. Under favourable conditions both the erumpent hyphae and those 
still in situ may form normal sporangia (Fig. 35 ). 
The formation of both pectin masses and endogenous hyphae seems in 
the case of Thraustotheca to result from localized mechanical injuries as 
well as from the effect of ionized metals or plasmolysis, which Horn (14) 
found to cause similar phenomena in Achlyapolyandra, de B. 
