16 THE SAPROLEGXIACEAE 



for the majority of the drawings, but many of the more recent ones have 

 been made by Mr. Couch. Plates 24 and 59 were prepared by Mr. F. A. 

 Grant, former Assistant in Botany. Miss Alma Holland, Assistant in 

 Botany, has inked in nearly all of the plates. 



Key to the Families of the Saprolegniales 



Threads of the plant (mycelium) not constricted into joints at intervals; oogonia containing 

 one or, more often, several to numerous eggs in the formation of which all the protoplasm 

 of the oogonium is used; eggs always smooth, not completely filling the oogonium 

 except in Leptolegnia; antheridia present in most species, but even when present 

 fertilization is not always effected; asexual spores biciliate, diplanetic or monoplanetic 



Fam. Saprolegniaceae (p. 17) 



Plant often with a distinct stalk, the threads constricted at intervals into joints, which in 

 the vegetative region are usually connected by small channels through the nodes; 

 oogonia and antheridia present in most species, the egg always single and with periplasm, 

 often with a sculptured surface; spores monoplanetic. .. .Fam. Leptoniitaceae (p. 169) 



Plant with a distinct enlarged stalk or, if the base is not distinctly differentiated, then branched 

 in a dichotomous or verticillate way; peculiar resting cells present which are probably 

 parthenogenetic eggs. These have thick, brown, distinctly pitted walls and completely 

 or almost completely fill the thin-walled oogonium, out of which they often slip at matur- 

 ity. Antheridia absent. Spores with one (or two?) cilia, monoplanetic. In one genus 

 {Allomyces) the plant body is divided into cells by cross walls, a condition unknown 

 in any other member of the order Fam. Blastocladiaceae (p. 180) 



Plant slender, branched, without a distinct stalk; not constricted into joints; egg single, 

 usually sculptured, in some species ripening outside the oogonium, fertilized by an active 

 sperm with one cilium. Spores uniciliate, monoplanetic. The family is by some authors 

 placed in an order of its own. It is distinguished from all other fungi by the retention 

 of an active sperm Fam. Monoblephariduceae p. 178) 



