APHAXOMYCES 163 



2. Aphanomyces scaber deBary. Jahrb. f. wiss. Bot. 2: 178, pi. 20, 



figs. 14-16. i860. 



Plate 50 and 56 



Hyphao dolicato, branching, about 5-7. 5;x thick, rarely as small as 2.5;x. 

 Sporangia like the hyphae, of indefinite length. Spores on encysting 

 about 9.5'^ thick; narrow and elongated in the sporangium. Oogonia 

 terminal on short or moderately long branches, very small, 15-23.71J. 

 in diameter, averaging al;oiit 2i.5;ji, in Xo. i of January 6, 1914, surface 

 uneven or varying to tuberculate, hut projections never so prominent 

 as in .-1. stellcitits; wall thin, not pitted. Eggs single, 1 3-1 8. 5[j. in diam- 

 eter, averaging about 15.5,1 in No. I of January 6, 1914, about 13.3:0. in 

 Xo. 8 of November 15, 1913, eccentric, a single large oil drop near one 

 side (our figs. 8-10 are not oriented to show the full eccentricity), proto- 

 plasm small in quantity and light in color, wall rather thick. Anther- 

 idia not seen in our form; present on most of the oogonia, according 

 to Fischer; not on all oogonia, according to Humphrey. 



Not rare at Chapel Hill; occurring in brooks and springs, as brook 

 below Howell's spring, brook behind athletic field, etc. Humphrey has 

 reported it from Massachusetts, where he also found a more spiny form. 

 For other illustrations see deBary ('81), pi. 6, figs. 30-36; and Hum- 

 phrey ('92), pi. 20, figs. 108-111. 



This species does not fruit so easily or abundantly as A. stellatus, 

 but is easily distinguished from it, when fruiting does occur, by the 

 small oogonia and eggs and by the much less papillate oogonia. From 

 A. laevis it differs in smaller eggs, rougher and smaller oogonia and ab- 

 sence of antheridia from all (in our form) or some of the oogonia. 

 On corn meal and egg yolk agar a strong growth occurs, but reproduction is absent. 

 On mushroom grubs in distilled water sporangia are produced but oogonia are rare. 



3. Aphanomyces stellatus deBary. Jahrb. f. wiss. Bot. 2: 178, pi. 19, 



figs. I- 1 3. i860. 



Plate 56 



Hyphae straight, delicate, little branched, about 5.5-6.5;! in diam- 

 eter, springing abundantly from the substratum, the tips rounded. Spor- 

 angia produced from the unchanged hyphae, very long, usually reaching 

 to the sidistratum. .Spores when in the sporangium irregularly rod- 

 shaped with une\cn ends, on escape becoming rounded and encysting 

 in an irregular group at the mouth of the sporangium, diameter 8-8.511. 

 (at times a few larger double ones ii-i2'^ in diameter mixed with the 

 others), emerging and swimming actively with the usual form, the large 

 c^'sts giving rise to two spores of normal size, according to deBary, 

 and confirmed by us. Oogonia subspherical, borne on rather long or 

 short lateral branches, normally covered more or less densely with con- 

 spicuous blunt papillae up to 5.5^1. long, diameter of the oogonia, including 

 the papillae, about 22-33;j.; walls rather thin, unpitted, cavity extending 



