WITH XOTES OIST OTHER SPECIES. 107 



called it S. Thureti, recognizing it as the form whose oogonia were first figured by 

 Thuret. But although, as has been remarked, the latter author had no understanding 

 of the true specific limits among these fungi, there is still no reason for refusing to 

 restrict to his form Gruithuisen's name, by which he called it, and which had previ- 

 ously been used in a much wider application. 



It has already been pointed out that the S.ferax (Gruith.) of Schroeter ('86) is 

 probably S. mixta DeBary, The description given in Saccardo's Sylloge ('88) under 

 the name of S.feraoi is quite unrecognizable. It is noteworthy that this work per- 

 petuates the old myth that Empusa is an imperfect state of S.ferax. 



It is difficult to circumscribe what DeBary has called xheferax group of Sap- 

 rolegnicE, since so many species show relations with each other at various points, 

 while remaining, within their limits, very constant. The three species already 

 described constitute, however, the most closely united group, and it is perhaps better 

 to limit the term to them, if it is to be used at all, than to apply it to an assemblage 

 of species necessarily much larger if at all increased. In these species, taken in the 

 order in which they are here placed, there is observed a pi'ogressive reduction in the 

 antheridia, and an increase in the normal size of the oogonia and in the number of 

 oospores ; while the average size of the latter varies little, although extreme speci- 

 mens may vary as much as 5/y. on either side of the average. 



Saprolegnia liypogyaa Pringsh. ('74). 



Syn. : S.ferax, var. hypogynaVv'mg&h.. ('74). 111.: Pringslieim, '74, PI. XVIII, Figs. 9, 10. 



This species, which has been studied by Pringsheim and DeBary ('88) and is 

 doubtless well founded, difiers from all other known Saprolegmacece in producing 

 antheridia without special antheridial branches. A second portion of the oogonial 

 branch is cut off just below the oogonium and constitutes the antheridium. Its 

 upper wall, which is also the basal wall of the oogonium, grows up, as a fertilization 

 tube, into the cavity of the latter. The oogonia show, in their form, in the pitting of 

 their walls, and in the structure and number of their oospores, near relations with the 

 ferax group, but the species is at once recognizable by the peculiarities above men- 

 tioned. It is not yet known to occur in America. 



Saprolegnia torulosa DeBary ('81). 



III.: DeBary, '81, PI. VI, Figs. 3-17. 

 PI. XVI, Figs. 46-49. 



Hyphse rather slender. Zoosporangia from cylindric becoming clavate, fusiform, 

 or nearly globular, often in torulose series. Oogonia globular, ovate, pyriforin, or 



