KING: CYTOLOGY OF ARAIOSPORA PULCHRA. 
235 
entire surface of the oospore except where the tube is formed. On 
the outside there is at this place, of course, no periplasmic wall. 
Furthermore, the inner wall is much, thinner here and from its 
arched appearance is evidently built out from the edges of the 
periplasmic wall of the inner end of the tube. It is possible that the 
wall of the germinating oospore ruptures at this point. 
Taxonomy. 
4 
Thaxter, who has carefully studied several of the Leptomitaceae , 
accepts Schroeter’s classification but states that the reproductive 
processes obtaining in this group connect them more closely with 
the Pythiaceae and Peronosporaceae. 
Trow (: 01 ) and Miyake (: 01 ) working independently on different 
members of the genus Pythium agree in their conclusions that 
the genus is nearer the Peronosporaceae than the Saprolegniaceae , 
and Trow proposes that Pythium be made coordinate with Albugo, 
Peronospora, and Phytophthora. 
An examination of the facts presented in this paper concerning 
Araiospora, shows conclusively that it is more closely related to the 
Peronosporineae than to the Saprolegniineae with which it has 
been associated by both Fischer and Schroeter. The general simi¬ 
larity of habitat, structure, and zoosporangium formation are the 
chief grounds upon which it could be placed with the latter group. 
On the other hand, there are many important facts that connect 
Araiospora with the Peronosporineae. The migration of the 
oogonial nuclei to the periphery where great numbers of them are 
cut off with the periplasm; the formation of a periplasmic cell wall 
upon which there are characteristic markings; the presence within 
the center of the oosphere of a highly specialized structure corre¬ 
sponding to that found in the Peronosporaceae ; the development 
of a well organized and functional receptive papilla; and,finally, the 
absence of an antheridial tube which is such a conspicuous organ of 
the Saprolegniaceae , all indicate that Araiospora’s affinities are with 
Pythium and the Peronosporineae. Accepting Trow’s arrangement 
of Pythium, the writer suggests that the Leptomitaceae as limited 
by Thaxter be taken from the Saprolegniaceae and placed, at least 
provisionally, as a separate family of the Peronosporineae between 
Pythium and the cohort Saprolegniineae. 
