102 The Journal 
RELATION TO EXTERNAL CONDITIONS 
The club-leaf disorder is manifested 
in many different degrees, depending 
upon external conditions and partly 
upon the variety. Though all of the 
plants become more or less abnormal 
in an affected area, individuals that 
stand side by side may show different 
degrees of deformity or reduction of 
the leaves, especially in the Chinese 
cotton and other unselected stocks. 
(See Figs. 1 and 2.) In severe cases 
all of the floral buds are aborted 
so that no more fruit can be set, and the 
crop is limited to the early bolls. Late- 
planted cotton suffers worse than early 
plantings, because there is less time to 
set a crop before the club-leaf begins. 
Plantings that fail to fruit early may 
remain completely sterile. With cooler 
weather in September or October, flow- 
ering and fruiting may be resumed, but 
the late bolls are not likely to open 
before frost. Hot weather in the spring 
is supposed to develop ‘the disorder 
early in the season, and the injury is 
worse in some years than it was in 
1919, according to native growers near 
Nanking. 
Little injury is done by club-leaf in 
the coast districts around Shanghai, 
Hangchow and Nantungchow, but very 
severe injuries were found at Wusih, 
Nanking, Anking, Wuchang, Nan- 
chang, and Yochow. In districts to the 
north of Nanking, as at Chuchow and 
Nanhsuchow, and north of Hankow, at 
Chengchow and Changteho, the club- 
leaf is generally present, but appears 
rather late in the season, so that the 
damage is not serious, and cotton is 
the chief crop in many districts. The 
country around Changteho, visible from 
the tomb of Yuan Shi Kai, appeared 
as an almost continuous cotton field. 
Around Peking and Tientsin club-leaf 
apparently ceases to be a factor of 
practical importance, only the last 
growth of the season being discolored 
or distorted. 
The relative immunity of the morc 
continuously humid rice country along 
the eastern coast may be explained by 
of Heredity 
facts noted at Nanking University, 
where one corner of the experimental 
field was in lower ground and shaded 
from the morning sun by the wall ofa 
compound and a row of trees. In this 
part of the field no symptoms of club- 
leaf disorder could be detected at the 
middle of August, though in other parts 
of the same field the disorder was 
strongly developed, and by the end of 
August it had appeared also on the 
later growth of the plants in the pro- 
tected corner. In another protected and 
somewhat shaded planting at Nanchang, 
some of the very late growth of the 
Upland varieties seemed to be entirely 
normal, although somewhat older leaves 
of the same plants were discolored and 
distorted. Z 
ro 
ABNORMALITY OF BRANCHING 
A general symptom of club-leaf is the 
development of many branches from 
buds that in normal plants would re- 
main dormant. Although vegetative 
branches usually are produced only 
from the lower joints of the main stalk, 
each leaf-axil contains a bud that may 
grow into a vegetative branch, follow- 
ing an injury or under conditions of 
luxuriance. In severe cases of club- 
leaf most of the axillary buds develop 
into branches, and even adventitious 
buds produce branches, sometimes four 
or five from the same node, a condition 
that might be described as abnormal 
proliferation or polyclady. The forma- 
tion of extra branches goes farther with 
the Chinese cotton than with Upland 
varieties, and produces the densely club- 
like masses of foliage which suggested 
the name of the disease. (See Frontis- 
piece and Figs. 1 and 2.) Upland vari- 
eties do not not form such dense masses 
of foliage, but retain a more open habit 
of growth as shown in Fig. 9. 
SHORTENING OF INTERNODES AND 
PETIOLES 
Another element of the changed 
appearance of the affected plants is 
the shortening of the joints of the stalks 
and branches, and the petioles of the 
