l6o THE SAPROLEGXIACEAE 



ing can be seen in it and the opening in the original membrane on the 

 oogonium can be easily made out (fig. 4). 



The oogonia are very rarely found. We had cultivated the plant for 

 about three months before the first oogonia appeared, and they were 

 matured during the Christmas recess. They have been produced only 

 two or three times since, and that only sparingly, notwithstanding our 

 efforts to induce sexual reproduction by cultures on various insects and 

 in different chemical solutions. The results of some of these experi- 

 ments are as follows: 



On gnat in .05% haemoglobin solution in shallow dish. Growth was about as extensive 

 as in water but there was a much more profuse branching, especially near the ends of 

 the hyphae. The difference was easily visible to the naked eye. No sexual reproduc- 

 tion. 

 On gnat in equal parts of haemoglobin .05% and Ca(N03)j .2%. .About twenty oogonia, 



all with antheridia. 

 Cultures made on gnats in shallow petri dishes gave no oogonia in any of the following 

 solutions (equal parts haemoglobin in .05% solution and chemicals in .2% solution 

 in distilled water in each case) ; 



Haemoglobin + KXOj 

 Haemoglobin + K(iHs(P04)2 

 Ca(N03)j 

 KXOs 



K6H3(PO02 



Cultures on gnats, flies, wasps, mosquitoes and spiders showed no noticeable difTerences. 

 Cultures under several inches of water were unfavorable for the formation of either sexual 

 or asexual reproductive organs. 



APHANOMYCES deBary, i860, p. 178. 



Hyphae very delicate, long, sparingly branched. Sporangia formed 

 from unchanged hyphae, long to very long, not proliferating within 

 old ones and rarely laterally from below. Spores borne in a single row, 

 emerging apically in elongated form, then rounding up and encysting 

 in a clump at the end of the sporangium as in Achlya, then emerging and 

 swimming again as in that genus. Specialized gemmae absent. Oo- 

 gonia terminal on short or long branches, smooth or warted, wall thin 

 and unpitted. Antheridia diclinous or androgynous, not a' ways pres- 

 ent. Eggs single, not filling the oogonium, eccentric, with a single 

 large fat drop in the protoplasm near one side or with a lunate disc 

 of oil droplets on one side. Fertilization has been proved in A. laevis, 

 which see for details. Spore development has been studied by deBary 

 ('60) and Rothert ('03). The genus shows a strong tendency to para- 

 sitism. 



Key to the Species 



Oo£;onial walls smooth, not with spines or warts; eggs 16. 5-26M thick 1 , , ,. .", , ,„, 

 ^ 1 r DO iA.helicoides{p.i69,) 



