132 THE LOWER FUNGI— PHYCOMYCETES 



The true nature of the sexual process in the group has been 

 only very recently elucidated by Kniep (1929). Working with 

 a hitherto undescribed species, Allomyces javanicus Kniep, he 

 has discovered a sexual process of so unique and distinctive a 

 type that on this basis alone the group is deserving of ordinal 

 rank. In this species the usual thin-walled sporangia and the 

 thick-walled resting sporangia occur, but in addition to these, 

 thin-walled sexual organs (gametangia) resembUng the sporangia 

 in shape are produced. The male and female organs, though 

 similar in shape, differ regularly in size. In both of them 

 uniciUate swarm cells termed gametes are formed. The larger 

 gametangium is regarded by Kniep as the female. The gametes 

 delimited in it are markedly larger than those formed in the 

 smaller male gametangium. After their escape from the game- 

 tangia the larger and smaller gametes fuse in pairs forming 

 bicihate zygotes. The zygote swims for a time, but finally comes 

 to rest, assumes a membrane, and puts out a germ tube which 

 develops directly into the rhizoid system which is to anchor the 

 new plant. Kniep applies the terms antheridium and oogonium 

 to the larger and smaller sexual organs respectively. 



Fusion of cihate gametes in pairs is not known to occur 

 elsewhere in the Phycomycetes above the level of the Chytri- 

 diales. There it has been observed in several species of Olpidium 

 and Synchytrium. In the Monoblepharidales the male game- 

 tangium frees wholly similar ciliate cells, but the content of the 

 female gametangium rounds up to form a non-ciliate practically 

 non-motile oosphere. As the Monoblepharidales and Blasto- 

 cladiales are admittedly closely related the discovery in other 

 species of these groups of intermediate types of sexuality would 

 not be surprising. Since, at present, the sexual process in other 

 species of the Blastocladiales is wholly unknown the acceptance 

 of heterogamic copulation of planogametes as the typical method 

 of sexuality in the group must be regarded as tentative. 



As Kniep finds the thick- walled resting sporangia also in Allo- 

 myces javanicus these structures are apparently of the nature of 

 chlamydospores and are hardly to be regarded as parthenogeneti- 

 cally developed oospores. 



Though the swarmspore is typically unicihate throughout 

 the order, occasional individuals with two or more cilia are 

 observed. Kniep has shown that these represent merely cases 



