430 AQUATIC PHYCOMYCETES 



For details of the morphology and development of this species see 

 Sparrow (he. eit.). The fungus may occasionally exhibit a Chytridium 

 habit of growth, that is, the sporangium may rest on the wall of the 

 integument (either inside or outside), the apophysis may be formed 

 within the wall material as part of the penetration tube, and the rhizoids 

 may extend out beyond. 



Two organisms of uncertain relationships have been referred to this 

 genus by Sparrow (1937a: 48, fig. 5); both of them inhabit insect 

 exuviae. 



The first, which was tentatively called Obelidium (?) mucronatum, was 

 found in caddis-fly integuments in Massachusetts. The sporangium was 

 broadly fusiform, 20-33 [x long by 7-8 [X in diameter, and rested on a 

 thick-walled cuplike base which was 3-4 \i in diameter. The apical region 

 was thin-walled and not prolonged into a mucro, the rhizoidal system 

 delicate, much branched, and radiating in all directions from a single 

 point on the base of the sporangium. Discharge of the zoospores was 

 not observed, although empty somewhat collapsed sporangia occurred. 



The second, called Obelidium hamatum, was found in midge exuviae 

 in New Hampshire and described as follows: 



"Main body of the sporangium extramatrical, broadly ovoid, thick- 

 walled, 8-9 [x in diameter by 8-12 \i in length, possessing a basal, thin- 

 walled stalk about 4 jx in diameter by 8-12 [x in length, continuous with 

 it, and on which are two oppositely placed, intramatrical spines; 

 rhizoidal system intramatrical, feebly developed, branched or unbranch- 

 ed, emerging from the abruptly tapering tip of the intramatrical part 

 of the stalk ; zoospores ellipsoidal, 4 [x long by 2 [x in diameter, posteriorly 

 uniciliate, uniguttulate, escaping by an opening at the base of the main 

 body of the sporangium. Resting spores not observed." 



Empty sporangia of this organism have been observed several times 

 since, in exuviae collected in Michigan. In these instances they were 

 entirely within the empty cavity of the exuviae. Once a single specimen 

 was observed lying free among the tangled threads of Mougeotia. The 

 new observations indicate that there is variation in the relation of the 

 fungus to the substratum. 



If further investigations seem to warrant the retention of these two 

 fungi in Obelidium a modification of the genus will be necessary for 

 their accommodation. 



