88 



Mycologia 



lows : A petri dish of sterilized agar-agar was inoculated with a 

 drop of water containing free spores. After a few hours the 

 spores sprouted. When the young fungus had grown sufficiently 

 to be discernible with the naked eye it was cut out, together with 

 the immediately surrounding medium and transplanted to a dish 

 of fresh agar-agar. When the growth had become quite robust 

 flies were inoculated, and fine cultures soon resulted. The spe- 

 cies was kept growing and under observation for the rest of the 

 term. 



The main hyphae of Thraustotheca are stout, straight, and pro- 

 fusely branching into secondary hyphae near their tips. The 

 secondary hyphae are much curved and twisted, and are often 

 curiously knobbed and gnarled as shown in fig. i. The main 

 hyphae reach a length of 2 cm. in strong cultures, and vary in 

 diameter from 20/x to T20/x averaging about 37/x. The sporangia 

 are borne terminally, the hypha continuing from a sub-sporangial 

 branch (fig. 2). The sporangia are typically short, broad, and 

 clavate, differing from the sporangia of any other of the Sap- 

 rolegniaceae. They vary from almost spherical on the one hand 

 to fusiform on the other. The spores encyst within the spo- 

 rangium immediately after they are formed. They are polyhedral 

 in shape, through pressure, each having a hyaline membrane of 

 its own (fig. 3). After the encysting of the spores, the sporan- 

 gial wall, which has always been thin, begins to disappear, van- 

 ishing first as a rule on one side near the end of the club, and 

 continuing to disintegrate until nothing is left of it except a nar- 

 row circular ring at the base. This basal ring may be quite con- 

 spicuous (figs. 4 and 5) or almost entirely absent. 



This method of dehiscence is entirely unique among the water 

 molds, and reminds us at once of the mold Mucor and its rela- 

 tives. This resemblance was remarked on at the time the plant 

 was described, and Solms-Laubach thought he saw another point 

 of agreement between Mucor and our plant in the outward bulg- 

 ing of the basal partition. This, however, seems to us to be 

 scarcely if at all noticeable in Thraustotheca. De Bary's figures 

 show it scarcely at all, and neither do ours. 



As the disintegration of the wall proceeds the spores fall apart 

 irregularly. They then emerge from their cysts and swarm in 



