1930] A New Species of Achlya 101 



(No. 6 of September 26, 1919), and in the same kind of material 

 from the branch in Battle's Park behind Dr. Pratt's residence (No. 4, 

 June 10, 1920). The description has been made from cultures de- 

 scended from a single spore. 



Our plant can be distinguished (with the unaided eye) from most 

 other Chapel Hill Achlyas by the network appearance given it by 

 the oogonia being scattered over the entire culture from the bases 

 of the hyphae to the tips. Achlya race))wsn approaches this network 

 appearance more than any other species of Achlya but in the latter 

 the oogonia are not nearly so abundant nor do they extend entirely 

 to the tips of the hyphae. In some species, such as Adilya oblongata, 

 the oogonia are borne in a definite zone near the substratum and 

 from half to two-thirds of the length of the hyphae from the tips 

 backwards are without oogonia. In the Prolifera group the oogonia 

 are scattered more or less over the entire culture but the big hyphae 

 and long sporangia dissipate the net work appearance. 



If we ignore the egg structure, the present species seems to be 

 closest to Achlya polyandi a Hildb. The two plants resemble each 

 other in the long, racemose oogonial branches which are recurved at 

 the tip ; in the often branched antheridial stalks which arise chiefly 

 from the oogonial branches ; and in the smooth oogonial walls which 

 are normally without pits except where the antheridia touch. The two 

 species are readily distinguished, however, by the difference in the 

 number of eggs in the oogonia, and in the size and structure of the 

 eggs. In Achlya polyandra the number of eggs varies from five to 

 twenty-five, the usual number being ten to fifteen, their average 

 diameter is 27ju, and they are said to be centric ; in A. orion the usual 

 number of eggs is one to two, the diameter of most 33-36ju,, with an 

 eccentric structure. In Achlya polyandra the sporangia are reported 

 as often not abundant, and secondary ones rare ; while in our plant 

 both primary and secondary sporangia are abundant. This species 

 is named for the nebula in Orion, which a photograph of the magnified 

 culture somewhat resembles. This photograph, together with draw- 

 ings by J. N. Couch will appear in a volume by W. C. Coker on the 

 Saprolegniaceae of the United States to be published soon. 



