36o 
WM. H. WESTON 
Obel (13), and others, had successfully induced the formation of 
sexual organs in other members of the family. Various concentra- 
tions of haemoglobin, of leucin, of potassium, sodium, and calcium 
phosphates, and of other substances were tested; but in no case was 
the production of sexual organs achieved. The effect of various 
temperatures and of changes in temperature was also tried; and the 
rapid or gradual drying of cultures was attempted. Moreover 
starving was resorted to, the fungus being grown on synthetic media 
containing a minimum of nutriment or on such natural substrata as 
pomace flies that had been thoroughly leached out and then dried. 
Dwarfed plants were produced, but no oogonia or antheridia developed. 
In all the cases above, a more or less copious formation of resistant 
spores resulted; but no production of sexual organs occurred. 
DISCUSSION 
The formation of bodies of non-sexual origin resembling to some 
extent the resistant spores of the foregoing description has been re- 
corded in nearly every genus of the Saprolegniaceae. In most of the 
cases on record these structures appear to be transient resistant stages 
which do not arise under conditions of the environment favorable to 
zoospore formation, but are induced by extremes of temperature, by 
foul water, or by other unfavorable conditions. As Klebs (7) has 
shown, the production of ''gemmae" (as he termed these structures) 
takes place when the fungus mycelium is subjected to conditions of 
environment permitting of growth and yet prohibiting zoospore 
formation. The conditions to which the Saprolegniaceae were sub- 
jected during investigation, before methods of pure culture were 
introduced, quite generally resulted in the formation of numerous 
structures of this sort. No reference to the occasional descriptions of 
these bodies need be made here, since the literature has been carefully 
covered in the monographs of Fischer (3) and von Minden (12). It 
may not be amiss, however, to recall one interesting instance discussed 
in an early paper by Walz (16). In Saprolegnia dioica Prings. he 
described a type of reproduction which at that time was unknown for 
the Saprolegniaceae, namely, the formation of the thick-walled bodies 
produced in basipetal succession at the ends of the hyphae. The 
resemblance between these structures (cf. Walz, Fig. 20) and the re- 
sistant spores of the Achlya described above (Figs. 6 and 10) is re- 
markably close. It would be of interest to know whether these bodies 
