1 64 THE SAPROLEGNIACEAE 



into the papillae. Eggs about i6-26[x thick, most about i8.5(jl, single 

 (rarely two — deBary), contents eccentric when fully mature, with an 

 inconspicuous lunate series of droplets on one side in optical section. 

 Antheridial branches androgynous or also from neighboring threads, 

 often branched. Antheridia short-tuberous, large, present on all or nearly 

 all oogonia. Fertilization uncertain. 



The species is typically saprophytic, but we have found it also para- 

 sitic on Achlya (see below). It is very plentiful around Chapel Hill in 

 springs, brooks, and creeks, occurring in about 25% of all Chapel Hill 

 collections. It has not been reported heretofore from America, but is 

 probably widespread. For other illustrations see Sorokine ('76), pi. 7; 

 jNIassee ('91), pi. 6, figs. 105-108. For cytological detail in an unnamed spe- 

 cies which maybe this, see Dangeard ('90), p. 117, pi. 6, figs. 18-23. It is 

 easily distinguished from A . laevis by its conspicuously papillate oogonia and 

 by the numerous antheridia of mostly diclinous origin. From A. scaber 

 it differs in the decidedly larger eggs and oogonia. Moreover, the walls 

 of A. scaber, while uneven, are much less papillate. Oogonia are abun- 

 dantly produced in all fairly normal condit'ons, as on animal and plant 

 bodies, nutrient agar, etc., in this respect differing from A. laevis 

 and A. scaber, where fruiting is rare. The antheridia are formed early 

 and reach the oogonia while the latter are still young and without their 

 papillae. We have not observed antheridial tubes, but they would be 

 difficult to see if present, and may be formed. The variation in the number 

 of antheridial branches is a marked characteristic. In a collection from 

 New Hope Creek no antheridia appeared in at least half a dozen cultures on 

 grubs in distilled water, but appeared abundantly on at least 90% of the 

 oogonia when grown on a lump of corn meal agar with grubs added in dis- 

 tilled water. On a piece of pea root growth was fairly vigorous, but even 

 more slender than on grubs; much branched; oogonia abundant, a good 

 many with antheridia. On solid corn meal agar growth was vigorous, 

 with oogonia in fair amount and antheridia on many of them. 



Abnormalities of the usual nature occur. Spores may be left in 

 the sporangia, particularly a few of the last ones, and may sprout there 

 through the wall to form a hypha or, according to Sorokine, the retained 

 spores may form short tubes and liberate spores as in Dictynchus. 



We have found several times in Chapel Hill a form of this species 

 differing from the typical only in being parasitic on species of Achlya. 

 The plentiful oogonia are borne both inside and outside the Achlya threads. 



With only the oogonia at hand, this species could easily be confused 

 with Saprolegnia asterophora. In the latter, however, both oogonia and 

 eggs average larger, antheridia are often absent, and the sporangia, of 

 course, quite different. 



