12 THE SAPROLEGNIACEAE 



tion from the cytoplasm of very little color. These elements have a 

 form so clear that it is sometimes difficult to distinguish them from 

 bacteria that are sometimes found collected on the wall of the fungus. 

 In certain filaments these chondriokonts undergo certain modifications 

 of form which also show in the living material; they can take the form 

 of short, thick-set clubs, of spindles, and even be transformed into 

 vesicles. It is difficult to decide whether these forms are in relation 

 to the cellular metabolism or represent alterations of the chondriosomes. 

 The chondriosomes show a greater resistance to the fixatives containing 

 acetic acid than similar bodies in general and than those of the other 

 fungi in particular." To summarize, Guilliermond finds in the Saprolegnia 

 studied : ist, chondriosomes quite characteristic and comparable to those 

 of the other plants and animals; 2nd, little fatty globules; 3rd, a system 

 of vacuoles filled with a substance endowed with selective power against 

 the vital stains, but which has not the characters of metachromatine. 



Aside from the dates and places of collection given incidentally and 

 usually in meager numbers by systematic writers, little is known of the 

 occurrence, periodicity and environmental factors involved in the growth 

 of the Saprohgniaceae. The one paper of importance dealing with these 

 subjects is by Petersen in his treatment of the Danish water molds ('10, 

 p. 504). His valuable notes are in most cases in agreement with our 

 experience. Certain differences are found and to be expected, due to 

 the cold climate of Denmark, as that the period of the Saprohgniaceae 

 begins in the spring and generally closes in November. With us there 

 is no closed season and we find water molds wherever the water is open 

 any day in winter. In Denmark Apodachlya is common, whWe Lept om- 

 it us is not recorded by Petersen. In Chapel Hill Leptomitus is very com- 

 mon, while Apodachlya has been found but once. 



Our experience clearly shows that vegetative threads and gemmae 

 are in all species killed by drying up, and that mature eggs may resist 

 drying. This is also the conclusion of Petersen. He makes the inter- 

 esting statement that while efforts to secure cultures from dry material 

 in many cases failed, yet growth had been obtained from material which 

 had been in a dried state for several years. As regards cold, Petersen 

 thinks that freezing for a short time need not have a deadly effect on 

 the mycelium, but that freezing for a long time is absolutely destructive. 

 We find that in all but one of the species (Pythiopsis cymosa) we have 

 tested, a culture allowed to freeze solidly over night is all killed except 

 the eggs. We also find, with Petersen, that darkness has no bad effect 

 on laboratory cultures. The greater abundance of individuals or species 



