22 THE SAPROLEGNIACEAE 



SAPROLEGNIA Nees v. Esenbeck, 1823, p. 513. 



Saprophytic on animal or plant remains, or parasitic in some species 

 on aquatic animals as fish, frog eggs, etc. Exposed hyphae branched 

 or more or less simple, straight or crooked, usually tapering gradually 

 outward, more or less pointed, springing from an intricately branched, 

 in part rhizoid-like mycelium within the substratum; all vegetative 

 parts colorless in transmitted light, white in reflected light, the threads 

 not septate or constricted until the approach of reproductive stages. 

 Sporangia at first terminal on main threads, typically long-clavate and 

 thicker toward the distal end, or at times slender- fusiform, often irregu- 

 lar and polymorphic in older cultures; at maturity opening typically 

 by an apical mouth, the spores emerging rapidly one by one through 

 pressure from within; typically proliferating within the older ones in 

 a "nested" fashion, but often also as in Achlya (see, for example, p. 26). 

 Spores pip-shaped, with two apical cilia, swimming away as soon as dis- 

 charged, soon coming to rest and encysting in spherical form; after a few 

 hours emerging again through a minute opening in the cyst and swimming 

 again more actively in a somewhat kidney-shaped form with two lateral 

 cilia, finally coming to rest on a nutrient substratum (if such is available) 

 and sending into it a slender tube which grows and branches into the ex- 

 tensive mycelium within. Resting bodies, called gemmae or chlamydo- 

 spores, of very variable shape and size formed in greater or less number; 

 often in chains like beads; after resting for a few days the contents pro- 

 ducing spores of the usual type which emerge by a variously formed mouth. 

 Oogonia terminal on main threads or on long or short lateral branches, 

 or in some species intercalary singly or in chains; shape spherical or oval 

 or pyriform or when intercalary sometimes fusiform ; wall smooth or papillate, 

 often pitted. Eggs one or many in an oogonium, formed of all its contents, 

 but never completely filling it, smooth, the protoplasm entirely surrounded 

 by one or two layers of fatty food material (centric or subcentric) ; under- 

 going a resting period before sprouting. Antheridia present or absent, of 

 various origin and appearance, usually terminating slender antheridial 

 branches which are short or long, simple or branched, and originating 

 from the same threads on which the oogonia they reach are borne (androgy- 

 nous), or from other threads (diclinous); antheridia when present often 

 forming one or more slender tubes which enter the oogonia through thin 

 places and reach the eggs. Fertilization has been shown to take place 

 in S. diclina and 5. mixta by Trow and in S. monoica by Claussen (see these 

 species for details). For a good account of spore development in 5. Jerax 

 see Rothert (1888). 



