oi.riDiopsis i,S5 



while the oogonia and the few antheridia which remaineil jiarth' empty 

 were stained a greenish brown. This contrast readily enables one to 

 distinguish sporangia from oogonia. 



Antheridia in all stages were observed: some full of pn)toi)lasm 

 and egg adjoining not formed; some partly empty and the egg beginning 

 to show' a clear space between itself and the oogonial wall, and some 

 entirely empty with the eggs formed. An antheridium one-third empty 

 was watched. Slowly the remainder of its contents passed into the 

 oogonium until about one-third of the original contents was left and 

 then a cover glass was dropped on the material. Immediateh' after- 

 wards i)art of the contents of the oogonium shot back into the anther- 

 idium, refilling it and demonstrating an open connection. 



The oogonial spines are so hyaline as to be barely visible in oogonia 

 which have just formed eggs, but they become much more obvious after 

 the eggs are a day old. Young oogonia stained with iodine show spines, 

 which otherwise would have been overlooked. 



Olpidiopsis Saprolegniae var. levis n. var. 



Plate 62, figs. 1-6 



Sporangia spherical to elliptic, smooth, very variable in size and 

 number, usually occupying the swollen ends of hyphae but not rarely 

 also in intercalary swellings; emptying by one or two tubes which pene- 

 trate the host's wall, but go little beyond and are usually short, at 

 times however as long or longer than the diameter of the sporangium; 

 spores very minute and numerous, probably with two cilia, swimming 

 rapidly, emerging at first through internal pressure and probably show^- 

 ing the same sequence as described in the preceding species, but not all 

 stages observed. Oogonia elliptic to nearly spherical, with the wall 

 rather thick and quite smooth and even; antheridial cells smaller than 

 the oogonia, smooth, thin-walled, one or tw'o attached to each oogonium, 

 their contents usually disappearing entirely by the time the oogonia 

 are mature. 



Parasitic on species of Saprolegnia as S. ferax, S. motioica, and 

 probably others. Found many times In Chapel Hill, as in the small 

 pond below Glen Burnie spring, where it may be secured almost with 

 certainty at any time a series of collections is made. 



The most important difference between this plant and 0. Saproleg- 

 niae is that the oogonia are smooth and seem to average smaller. In the 

 latter they are densely covered with warts or spines. This difference is 

 striking and will make it necessary to consider our plant a variet}'. The 

 two species of this genus with smooth oogonia that are so far described 

 are parasitic on algae (see Fischer, '92, p. 37). 



