42 THE SAPROLEGNIACEAE 



etcr, one to 30 in an oogonium, and in absence of oogonia in chains.* 

 Anthericlia scarce, only two seen and these dichnous. Found on a Hving 

 pike in Switzerland. This may be the same as 5. lapponica (see p. 73), 

 but that is said rarely to have oogonia terminating the main branches. 



Saprolegnia hodanica Maurizio is another plant that seems almost 

 exactly like our Chapel Hill S.ferax: Threads slender, main ones 31-47^1 

 thick, often with cellulose grains which may stop up the small threads 

 as in Leptomitus. Oogonia racemose, rather seldom intercalary, never 

 in chains; wall thin, colorless, with numerous small pits; oogonia 54~93iA 

 thick, the oblong ones SSxioSfj.. Eggs 23.5-31^1. thick, 4-30+ in an 

 oogonium. No antheridia. 



Saprolegnia ferax cannot be limited to forms without antheridia. 

 DeBary admits the presence of some antheridia as does Humphrey also, 

 but it would appear from the work of Pieters and myself that antheridia 

 are frequently present on as many as 10-15% of the oogonia. Pieters 

 (Mycologia 7: 310. 1915)! has found that in his strains from Ann Arbor 

 grown on fly at room temperature and in cooler temperature (i2°-i5° C.) 

 the number of oogonia with antheridia varied from 0-19% (see his pi. 170, 

 fig. i). For other experimental work in this species see Pieters ('15b). 

 In his studies on the physiology of Saprolegniaceae (Ann. Bot 22: 361. 

 1908) Kauffman supposes a strain of his from Ann Arbor to be S. mixta 

 because it contained a few antheridia, i or 2 per cent normally. This 

 must be considered S. ferax if the latter and S. mixta are to be kept 

 separated at all. In experiments with his strain he increased the pro- 

 portion of anthcridia-bearing oogonia to 25% both in leucin + potassium 

 sulphate and in haemoglobin + potassium nitrate. In haemoglobin + 

 calcium nitrate, on the other hand, there were no antheridia on the 

 abundant oogonia. For cytological data see Dangeard ('90), p. loi and 



('16), p. 87. 



Trow has shown that in material that he calls S. Thureti or S. mixta, 

 depending on the absence or presence of antheridia, the unfertilized eggs 

 are uninucleate as in other species and are without nuclear fusions in 

 his opinion ('95, p. 637). In all respects except fertilization the cyto- 

 logical phenomena are alike. See S. mixta for some detail. 



*0f the typical form of S. ferax Maurizio says the oogonia are often in chains, eggs 3 

 to about 50, 23-26.5^1 in diameter (Jahrb. f. wiss Bot. 29: 93. 1896). Minden says (1. c. 

 p. 521) the oogonia are seldom intercalary in chains, the eggs 20-271J, in diameter, not rarely 

 (iver 40-50 in an oogonium. Oogonia in chains are not mentioned by deBary. Pringsheim, 

 Humphrey or Fischer (the latter giving the eggs as 20-271X thick). To separate new species 

 on absence of such chains would seem, therefore, to be poor judgment. It may be said 

 that Maurizio's work gives many indications of inferiority. 



fAlso listed in Ann. Mich. Acad. Sci. 17: 195- 1915. as 5. Thureti. 



