84 THE SAPROLEGNIACEAE 



more careful study 5. tonilosa will be found to belong to this genus. 

 See S. rhaetica and 5. variabilis which are also near. 



In the character and extent of its mycelium and in some other char- 

 acters also this species is most like 5. delica. The few and always di- 

 clinous antheridia are the most striking character distinguishing this 

 from S. delica. Another difiference is the more hyaline and more quickly 

 disappearing antheridial branches, which are more difficult to trace than 

 in S. delica and S. anisospora. Moreover, the antheridia when present 

 are rarely over one or two and are never numerous enough to cover or 

 almost co\'er the oogonium, as is so often the case in 5. delica and S. 

 anisospora. Nearly all the antheridia are found in the denser, central part 

 of the culture, the long and conspicuous antheridial branches, winding 

 about the periphery in S. delica, being absent. Another difiference from 

 the latter is found in the frequent appearance of oogonia on short branches 

 from just below the terminal ones, and also in the rather constant ap- 

 pearance of a number of oval or pointed or otherwise irregular oogonia 

 in each culture. From S. diclina it is easily separated by the few an- 

 theridia, fewer eggs and much less abundant gemmae. From S. ferax, 

 which may ha^'e about the same proportion of antheridia, it differs in 

 having smaller oogonia, with fewer and far less conspicuous pits, much 

 fewer cj'lindrical oogonia, diclinous antheridia and fewer eggs. In the 

 same way it differs from 5. mi.xta, if that is a good species. 



The oogonia have a pitted appearance when the protoplasm is pre- 

 paring to divide, just as in many other species. These spots are ap- 

 parently oil drops or vacuoles just below a surface layer of protoplasm, 

 and have no correspondence to the real pits that appear later. 



At temperature of 79° F. the spores are expelled with force in a 

 semitorpid state, gather strength after a few seconds of slow movement 

 in an open cluster and then swim off. They are popped out with vio- 

 lence a distance of one-fourth to one-half the length of the sporangium, 

 although almost dormant — a sure evidence of internal pressure being the 

 cause of emergence. 



The following cultures were made from No. 8 of March 8, 1918: 



In .05% haemoglobin solution on house fly the growth was only fairly vigorous. Many 

 oogonia, but few antheridia. Few sporangia. The oogonia initials form readily 

 enough in haemoglobin solution, but the eggs do not round up until the growth is 

 transferred to pure water. 



In equal parts of .05% haemoglobin solution and .25% NaHjPOj on fly. Growth quite 

 vigorous, more so than in any other of the solutions tried, many oogonia formed and 

 many antheridial branches, but few, in comparison to the ones formed, were applied 

 to oogonia. A good many empty sporangia seen. As in above experiment no eggs 

 were formed until culture was transferred to pure water. 



