RELATION BETWEEN VEGETATIVE VIGOR AND REPRODUCTION 533 
Two of these belonged to the genus Saprolegnia. S. ferax (Gruith) 
Thuret was collected at Heidelberg in the fall of 191 1; S. monoica 
Pringsh. was secured from alga material out of pools near Ann 
Arbor. Achlya racemosa Hildebr. was collected at Heidelberg and 
was unfortunately lost in a fire which destroyed a large part of the 
botanical laboratories at Ann Arbor in the spring of 191 3, at which 
time also a large number of notes and other records were lost. The 
records of this species are therefore incomplete. Achlya prolifera 
De Bary was obtained from alga material out of pools near Ann 
Arbor. Physiological studies on several other species, together with 
descriptions of some new species and remarks in regard to certain 
points of relationships, will be discussed in other papers. 
Methods 
For isolating the forms Kauffman's ('08) method of single spore 
cultures was strictly followed. While the writer is not disposed to 
say that men like Maruzio ('94) and Obel (1. c.) did not work with 
pure cultures it seems more than likely that the results claimed to 
have been gotten by Lechmere ('11) may be due, in part at least, to 
mixed cultures. Moreover, a writer with so little appreciation of the 
worthlessness of sporangia and gemmae as specific characters, ^ can 
hardly be taken seriously when he states that the sporangia charac- 
teristic of six different genera were found in one supposedly pure 
culture. While Lechmere says that he used Kauffman's method he 
has apparently quite overlooked the fact that the essential part of 
this method is the isolation of one spore; it does not appear that he 
attempted to do this in his work. 
All the cultures of each species made in connection with the present 
problem were descended from an original single spore and if there was 
the slightest reason to doubt the purity of a culture, a single spore 
culture was again made and carried through on a fly, so that the 
specific characters might be compared with the original. All the 
species that were not being used for experimental work were kept 
alive on flies or in pea extract. In either case cultures can be set 
aside for two or three months without any danger of loss. 
2 See 1. c, p. 176, where Lechmere concluded that two species of Saprolegnia 
were identical because of the similarity of habit, gemmae, and shape and peculi- 
arities of the sporangia, although the one produced oogonia readily and the other 
did not produce them at all. 
