l8o THE SAPROLEGNIACEAE 



plasm into the water, the remainder (larger part) forming the egg which 

 matures within the oogonium. 



D. insignis (Thaxter) Lagerheim (p. 40). Massachusetts and Maine. 

 D. fasciculata (Thaxter) Lagerheim (p. 40). Massachusetts. 



BLASTOCLADIACEAE 



This family has been based on a single genus, Blastocladia, whose sys- 

 tematic position has been and still is somewhat doubtful. Thaxter ('96) 

 thinks that the genus should be placed either under the Pythiaceae or in 

 a new family of its own. Minden ('12, p. 506) and Petersen ('10, p. 

 532) recognize the family Blastocladiaceae and it would seem as well to 

 follow them for the present. We are also including in the family the genus 

 Allomyces Butler, placed by the author in Leptomitaceae. Except for a 

 few additions made to include Allomyces the following diagnosis is taken 

 with a few changes from Minden: 



Saprophytic fungi living in water on substrata of plants. Mycelium 

 unicellular, or in Allomyces with complete septa at the nodes, rather 

 abundantly branched, separated usually into a main axis and secondary 

 axes and sometimes having sterile, thin threads of unknown function. 

 Sporangia usually ellipsoid to cylindrical in shape, often clearly forming 

 sympodia through the shortening of the threads upon which they grow, 

 but also thickly crowded together, seldom growing through each other. 

 Zoospores ellipsoid to egg-shaped with broad blunt ends and one (or 

 two?)* cilia on the broader, colorless end, the other end containing 

 small granules; emerging with force through an apical opening in the 

 sporangium and swimming away, then, after being surrounded by a mem- 

 brane, sprouting; while entering into the resting condition there is amoe- 

 boid motion. Sexual reproduction does not take place. Instead there 

 are formed resting bodies in the shape usually of broad ellipsoid 

 cells that coincide in origin and position with sporangia, but have a 

 membrane consisting of two sheaths of which the outer one is smooth 

 and colorless while the inner one appears finely and regularly dotted (or 

 punctured). At maturity these cells either fall away as a whole or the 

 thin, colorless, outer sheath splits at the tip and allows the escape of the 

 inner sheath and its contents. After a time the resting cells germinate 

 by the cracking of the thick brown wall, so as to allow the protrusion of 

 a delicate bladder in which the spores develop. Spore discharge, how- 

 ever, has not yet been observed. 



BLASTOCLADIA Reinsch, 1878, p. 291. 



Characters of the family except that the plant body is never septate. 

 Four species have been described, all of which are treated in Minden 's 



* Thaxter finds zoospores to have two cilia as a rule in B. Pringsheimii. 



