LEPTOMITALES 89 



currence. The only monographic treatment is that of Kanouse 

 (1927). 



Leptomitus, the type genus, contains but a single species, L. 

 lacteus. It occurs in se\va2;e effluents in waters containing Indus- 

 trial wastes of various kinds and may occasionally be found grow- 

 ing en Jimsse in clogged drains and similar places. Detailed stud- 

 ies of the nutrition of this species have recently been made by 

 Schade (1940), and Schade anci Thimann (1940). 



The thallus of Leptomitus is filamentous and constricted, and 

 sporangia are not differentiated as such. The segments become 

 transformed into sporangia in basipetal succession and liberate 

 the biciliate zoospores either through a pore in the terminal seg- 

 ment or through a number of pores, one in each segment. Sex- 

 ual reproduction is unkno\\'n in the genus. 



Apodachlya bears considerable resemblance vegetatively to 

 Leptomitus, but the segmented hyphae bear pyriform sporangia, 

 whose zoospores may either s\\ im away directly or remain en- 

 cysted for a time at the mouth of the sporangium. Sexual repro- 

 duction occurs by means of a terminal oos^onium subtended by 

 a hypogynous antheridial cell [Kevorkian (1935)]. The devel- 

 opment of the oogonium differs from that of other representa- 

 tives of the order in that no definite periplasm is formed. It has 

 therefore been suggested that Apodachlya and the aUied Lepto- 

 mitus are more closely related to the Saprolegniales than are the 

 remaining genera of this group. 



In the Genus Sapromyces the thallus is of the arbusculate type, 

 consisting of a trunk or basal cell and numerous branches, but 

 there is very little difference in size between trunk and branches. 

 Sporangia, lobate to cylindrical in shape, occur terminally or 

 near the constrictions of the branches and liberate the biciliate 

 zoospores. The genus has two species, S. audrogymiSy which is 

 homothallic, and S". reinschii, which is heterothallic. In both 

 species the oogonia are pyriform and contain a single oospore 

 surrounded by periplasm, according to cytological investigations 

 of Kevorkian (1935). Bishop (1940) has recently demonstrated 

 the occurrence of relative sexuahty in 5. reinschii and has grown 

 this organism in pure culture. 



In Araiospora and_ Rhipidium, both of which have several 

 species, there is a stout trunk with rather slender, constricted 

 branches. As in Sapromyces, the trunk is attached to the sub- 



