[Vor. 3 
44 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
In the field it was noted that the plants of the resistant 
strains of cabbage were, as a rule, larger than plants of the 
commercial strains of the same age. The first year it was 
thought that this difference in size might be due to crowding 
in the seed-bed of the plants of the commercial strain, chiefly 
beeause the amount of available seed of the resistant varie- 
ties was limited, 
while that of the 
commercial strain 
was plentiful. When 
this faet repeated it- 
self over three years, 
experiments in the 
laboratory were run 
7. Fungous hyphae obtained by disseetion of to account for the 
diseased stem after boiling in KOH solution. Camera difference. Seeds 
lucida sketeh. 
were placed between 
moist filter paper in petri dishes and allowed to germinate. 
Twenty-five seeds were placed in each dish, and two dishes of 
each strain, VIII a-16 and commercial Danish Ball-head, were 
germinated. After wetting up the filter paper with distilled 
water the dishes were all placed in an incubator at 22°C. The 
seeds of the resistant strain germinated twelve hours before 
those of the commercial varieties, three days after the begin- 
ning of the experiment. Plate 2, figs. 5 and 6 give an idea 
of the appearance of the seedlings at this time, under similar 
conditions of moisture and temperature. 
This characteristic of growth suggested that there might 
be a considerable difference in osmotic pressure between the 
root cells of the two strains, and experimental work was un- 
dertaken to determine whether the threshold of plasmolysis 
of the two strands differed toward NaCl solution as a plas- 
molytie agent. Two trials were made using the root-hairs 
as indicators, but in neither case was any difference between 
the threshold of plasmolysis of the resistant strain and that 
of the susceptible strain found. 
