30 THE LOWER FUNGI—PHYCOMYCETES 



may fairly be regarded as intermediate between the planogamic 

 copulation of isogametes in Olpidium or Synchytrium, and 

 heterogamic copulation as it exists in Monohlepharis where the 

 female gamete is practically non-motile and spherical. Since 

 in other respects the Blastocladiaceae and Monoblepharidaceae 

 are clearly closely related a similarity in their sexual process is 

 not surprising. 



The type of heterogamic copulation represented by Mono- 

 hlepharis is clearly higher than that in Allomyces in that the 

 gametes are easily distinguishable as male and female respec- 

 tively. They are not merely dissimilar in size. They differ 

 in other respects as well. From the beginning the female game- 

 tangium is uninucleate. Finally its contents contract to form 

 a single, large, spherical, naked, non-ciliate and practically non- 

 motile gamete, which is here called the oosphere. The male 

 gametangium is smaller than the female and of a somewhat 

 different shape. At maturity it frees several uninucleate, 

 unicihate gametes. These swim about actively and are attracted 

 to the oosphere. They are termed antherozoids (sperms, 

 spermatozoids). An anthcrozoid, on coming in contact with 

 the oosphere, fuses with it, and its nucleus approaches and 

 unites with the female nucleus. This fusion of the sexual nuclei 

 is termed fertilization, and the female nucleus is said to have 

 been fertilized. Following fertilization the oosphere assumes 

 a wall, and thereafter is called the oospore. The oospore 

 functions as a resting spore, and, after a period of quiescence, 

 puts out a germ tube which develops into a new thallus. 



The female character of the oosphere is evident in that it 

 is functionally the receiving cell, remaining passive until ap- 

 proached and fertilized by the male gamete, and in that it 

 has, thereafter, the capacity for developing into the new plant. 

 The gametangium which bears the oosphere is from that fact 

 alone clearly the female, and may be called without hesitation 

 the oogonium. The antherozoids are surely male in that they 

 effect fertilization of the oospheres. The gametangium in 

 which they are formed is consequently male and is termed 

 the antheridium. The larger size of the female gamete and 

 gametangium is pronounced and corresponds in general with 

 the situation in all higher oospore-forming Phycomycetes. 

 Monoblepharis is noteworthy in that it is the only genus of the 

 known Phycomycetes in which ciliate male gametes fertilize 



