1915] PIETERS—ACHLYA AND SAPROLEGNIA 485 
mosa, and a number of species of Saprolegnia had been cultivated, 
but none of these produced sporangia in 1.5 per cent agar with pea 
broth. In the fall of 1913 nos. 67, 68, and 70 were isolated, and in 
every case the germ tube gave rise to several vigorous hyphae which 
produced sporangia after attaining a length of some 5 mm. 
It was also found that sporangia were sometimes developed on 
mycelia growing in liquid pea broth. Since there certainly was no 
question here of an abundant supply of food, the thought suggested 
itself that Kiess’s conclusion, that sporangium formation takes 
place only when there is a dearth of food, would not apply to 
all species. However, when mycelia were transferred to purified 
water, sporangia were normally produced. 
The hypothesis suggested to explain the facts was that although 
there was plenty of food it did not reach the surface of the growing 
hyphae rapidly enough; these were therefore soon in an environ- 
ment poor in food and then sporangia were normally and inevitably 
produced. 
In the pea broth the proteid constituents are colloids, and these 
large molecules diffuse with extreme slowness, so slowly, in fact, 
that their movement can be considered to be practically nil. The 
large, vigorous hyphae which require a relatively large amount of 
food would therefore after a time find themselves surrounded by a 
film of liquid out of which they had absorbed the food particles 
and to which diffusion did not carry new particles as rapidly as the 
hyphae used them. This condition would result in starvation and 
the development of sporangia. 
To test this hypothesis several series of experiments were pre- 
pared as follows. Four Ehrlenmeyer flasks, each holding 100 cc., 
were half filled with pea broth, sterilized, and inoculated with 
A. Klebsiana. One of these was so hung by a stout string that an 
arm clamped to a shaft and protected by a cotton pad pushed the 
flask aside about once a minute. As the flask was pushed aside, 
it fell against the cotton pad on the end of the arm and thus the 
liquid was vigorously jarred. Another flask was placed upon a 
shelf subject to a slight jar from a small motor, so that the surface 
of the liquid could be seen to tremble slightly; the other flasks were 
placed upon the writer’s desk. 
