te sh ae 
RUSSELL COTTON AT WUCHANG, CHINA 
The club-leaf disorder has affected the plant 
in its later growth as shown at the top 
contrasting with the older normal leaves 
below. (Fig. 2) 
tions are reversed in respect to reduc- 
tion and distortion, which are less than 
in the Upland cotton, and much le 
than in Chinese. Another difference is 
that the margins of affected Sea Island 
and Egyptian leaves usually curve up- 
ward, so that the lobes become more 
deeply channelled instead of being 
turned under. The Egyptian cotton at 
Nanking was nearly defoliated by the 
black-arm or angular leaf-spot disease, 
which also attacked the young involucral 
bracts, so that only a few bolls de- 
veloped. This was in striking contrast 
with the Sea Island cotton in the next 
row, which remained vigorous and leafy 
and developed a goods crop of bolls, 
though only a few were open at the end 
of October when frost was expected. 
The Upland cottons were less affected 
by angular leaf-spot than*the Egyptian, 
though more than the Sea -Island, 
while the Chinese cotton seemed not to 
be attacked. 
DEVELOPMENT OF IMMUNITY BY 
SELECTION 
A disorder that cripples the plants 
and distorts the leaves undoubtedly 
108 
A LONE STAR COTTON PLANT 
This plant, at Nanking, China, shows club- 
leaf in its later growth in contrast with the 
normal leaves of older growth. (Fig. 8.) 
must increase the difficulty of selection 
and roguing, which are necessary to 
develop and maintain pure stocks of 
seed, but a possibility of developing 
immune varieties of the Chinese cotton 
is indicated by individual differences 
of reaction to the disorder that were 
noted in many cases. At Nanking a 
Chinese variety with red leaves showed 
much less reduction and distortion of 
foliage and grew to twice the size of 
the neighboring green-leaved plants. 
Another Chinese selection with very 
pale foliage and small white, unspotted 
flowers that did not open widely, 
showed a very extreme form of club- 
leaf injury. On the other hand a na- 
tive grower east of Nanking consi- 
dered a “purple-stem” strain of the 
narrow-leaved ‘‘chicken-foot’” cotton 
more susceptible to the “wilt” than a 
“ereen-stem’’ form. At the Wuchang 
Experiment Station many plants of a 
slender, hairy, Indian variety did not 
appear to be affected at all by club- 
leaf, although the neighboring rows of 
Chinese cotton were very badly injured. 
