148 THE SAPROLEGXIACEAE 



"Sporangia in plain cymose arrangement, spindle-shaped, relatively broad, 36-80^1 long. 

 Oogonia 75-iooix long, 45-1 I0[i broad, numerous, ellipsoidal in outline, but set with large, 

 irregular, scattered, hollow projections 5-1811. long. Eggs spherical, 3.5-7(1. thick [probably 

 misprint], Antheridia absent. With S. monoica on a sink carp." 



Minden says that he has not seen the Polish paper, but thanks Professor Lindau for 

 the information, and adds: "In the form of the oogonia apparently near A. cornuta Archer 

 and A. Hojeri Harz. " Under the last species he says that it may be identical with A. 

 Nowickii. 



Achlya sp.? 



Tiesenhausen ('12, p. 288, no figures) describes a sterile form that he does not try 

 to place. It is notable, he says, for the great variety of forms assumed by the h>phae. 



THRAUSTOTHECA Humphrey, 1892 [1893]. p. 131. 



Main threads stout, branching; sporangia terminal, stout, typically 

 short-clavate, liberating the spores by cracking and disintegrating; spores 

 encysting before escaping and remaining clustered where liberated, af- 

 ter a rest escaping and swimming with two lateral cilia, again coming 

 to rest and encysting before sprouting. Oogonia single, commonly ter- 

 minal on short lateral stalks, spherical, smooth, weakly pitted or with- 

 out pits; eggs rather few, eccentric. Antheridia diclinous, occurring 

 on all oogonia. Fertilization probably occurs but has not been demon- 

 strated. There is but one species (but see Achlya diihia). 



Thraustotheca clavata (deBary) Humphrey. Trans. Am. Phil. Soc. 

 17: 131. 1892 [1893]. 

 Dictyuchus clavatiis deBary. Bot. Zeitung 46: 649, pi. 9, fig. 3. 



Plate 51 



Main hyphae stout, straight, reaching a length of 2 cm. in strong 

 cultures and a thickness of 20-i20tJ,, averaging about 37^1; profusely 

 branching into secondary hyphae near their tips; secondary hyphae 

 much curved and twisted, and often curiously knobbed and gnarled, 

 as shown in fig. i. Sporangia 37-85 x 66-370U., terminal or rarely inter- 

 calary, proliferating as in Achlya, usually short, broad, and clavate, but 

 often elongated somewhat as in Pythiopsis or even as in Saprolegnia, 

 varying from nearly spherical to fusiform, differing from the sporangia 

 of any other of the Saprolegniaceae. Spores about i2.5yL thick, en- 

 cysting within the sporangium immediately after they are formed, and 

 liberated passively and slowly by the gradual cracking and disintegration 

 of the sporangium wall, which is probably due to internal pressure. They 

 now emerge from their cysts and swim actively in a laterally biciliate 

 form, encyst again and sprout. In the sporangium they are polyhedral 

 in shape, through pressure, each having a hj'aline membrane of its own. 



*The species was really first published incidentally by Biisgen in 18S2, p. 261, pi. 12, 

 figs. 1-8, who in his study of the development of the sporangia described it sufficiently under 

 the name of Dictyuchus clavatus deBary sp. nov. 



