166 
Weston.—The Development of 
of the antheridia. No exception to the foregoing condition has been noted 
in a large number of cases ; and the figures of Coker and Hyman ( 9 , Fig. 8) 
and of Horn ( 14 , Fig. 19) in the case of Achyla polyandra, de Bary, strikingly 
corroborate the writer’s observations on this point. The parthenogenetic 
formation of oospheres would, of course, be a serious objection to this inter¬ 
pretation. No such cases were observed, however, under the usual culture 
conditions, nor could parthenogenesis be induced by the method Trow ( 29 ) 
found successful in the case of Achyla americana var. cambrica. 
When the oospheres have been formed, the oogonium wall, especially 
when turned red by chlor-iodide of zinc, is seen to be smooth, thick, and 
definitely pitted. The character of the pitting varies under different 
conditions, since, on impoverished mycelia, the oogonia show the weak 
pitting (Figs. 49, 53, 63, and 64) which has been considered of diagnostic 
value by previous investigators, while on vigorous mycelia the oogonial 
walls are marked by large and numerous pits (Fig. 51). It is of interest to 
note that Horn ( 14 ) found a similar variation in the pitting of oogonia 
in Achlya polyandra , de Bary. 
After the oospheres are differentiated, they undergo a period of 
maturation (Figs. 54 to 58), the wall increasing in thickness and the proto¬ 
plasmic contents separating out as the oil droplets fuse together. Finally 
the structure of the mature oosphere is attained, characterized by a thick, 
unroughened wall within which the protoplasm is condensed into a bowl¬ 
shaped granular mass partly surrounding a large, slightly flattened oil 
globule (Fig. 58). This eccentric arrangement of the oospore content may 
persist for months ; hence, in the case of Thraustotheca at least, Maurizio’s 
(20) objection to the term eccentric as representing only a transient 
condition seems groundless. 
Among the maturing oospheres, especially after staining, can be seen 
slender fertilizing tubes which arise from the antheridia, and enter the 
oogonia through the pits in the wall (Figs. 50 and 51). In contrast to the 
thickened antheridial walls, which show the same composition as those 
of the oogonia, the delicate fertilizing tubes are of cellulose. It is worthy of 
note that the fertilizing tubes were never seen to penetrate the oospheres, 
nor was any sudden passage of material down the tubes observed. 
Germination of the Oospores. Germination of the oospores of Thransto- 
theca has not been observed by previous investigators. Germination was 
induced by the writer, however, by placing mature spores in pure water 
maintained at a temperature optimum for growth {circa 25 0 C.). Under 
these conditions the protoplasmic content increases in extent, probably 
at the expense of the oil globule, which becomes irregular (Fig. 59) and 
gradually disappears. The wall, meanwhile, first swells (Fig. 59), and 
is resorbed and distended until it becomes comparatively thin (Fig. 60). As 
a result of these modifications the resting oospore, of about 17 in diameter, 
