320 



Mycologia 



abundantly pitted walls; thus uniting the characters of A. proli- 

 fera and A. DeBaryana. 



From the work of Horn,^ Peterson,* and myself it has now 

 become evident that it is no longer possible to distinguish clearly 

 between these species as established by DeBary and Humphrey. 

 Forms are appearing constantly that combine their qualities in so 

 confusing a manner that it is impossible to refer them with cer- 

 tainty. For example, Horn says (1. c, p. 224) that while the 

 plant he describes is undoubtedly near A. DeBaryana (A. poly- 

 andra as he calls it), it cannot with absolute certainty be said to 

 be identical with it; for while in A. DeBaryana the antheridia are 

 mostly of androgynous origin, in his plant they are mostly diclin- 

 ous. He also finds that when cultivated in peptone and in grape 

 sugar or cane sugar certain oogonia show numerous pits. 



In his work on Danish Fresh-water Phycomycetes, Peterson 

 (1. c, p. 524) finds, of these three species, only A. americana. 

 He places it as a form of A. DeBaryana (A. polyandra, as he 

 calls it) not as a species, saying that ''The reason I do not make 

 use of Humphrey's species-name, but place this species as a 

 variety of Achlya polyandra is that I am inclined to regard these 

 pores as variable characters, as there are always some oogonia 

 which have fewer pores than others." 



Neither Achlya prolifera nor A. DeBaryana has so far been 

 described from America. A form that is one or the other or 

 both of these has appeared in my cultures at Chapel Hill for a 

 number of years. It is by far the most abundant Achlya in our 

 territory and may be had from springs, ditches and pools at any 

 time of the year. During the spring and summer of this year 

 (1912) I carefully studied the plant in pure cultures from a num- 

 ber of different collections. 



To the naked eye, the species may be easily distinguished from 

 others by the very large chlamydospores that usually make a 

 white fringe at the periphery of the cultures. These are often 

 arranged into groups that resemble the branching horns of a 

 deer (fig. i), or they may be shaped more like a section of Hala- 

 nieda (fig. 2). In mature cultures the hyphae become divided up 



^ Annales Mycologici 2 : 207. 1904. 

 * Annales Mycologici 8: 294. 1910. 



