16 BULLETIN 24, U. S. DEPARTMENT OF AGRICULTURE. 
age, and continue to bear vigorously throughout most of their exist- 
ence. The trees of the two sexes are usually unevenly distributed, and. 
female trees may sometimes be greatly outnumbered by males. The 
seed matures, as a rule, during May or early June, when the capsules 
open. 
‘The seeds are very minute, usually about an eighth of an inch long, 
and sometimes no more than one-twelfth of an inch wide. They are 
oblong, obovate, rounded at the apex, rather light brown in color, 
and are surrounded at the large end with a fringe of long, white, 
silky hairs which gives them a characteristic cottony appearance and 
renders them extremely lght and buoyant. Seed dissemination, 
therefore, takes place easily, the seed often being carried by the wind 
miles from the parent tree. Seed dispersion is also effected by the 
overflow waters, which frequently leave fertile seed on the muddy 
alluvial deposits far from the parent tree. 
The germinating power of freshly collected mature cottonwood 
seed is comparatively high, varying from 60 to 90 per cent. With 
proper moisture conditions the seed germinates very quickly. The 
vitality of the seeds, however, is very short-lived, few, if any, ger- 
minating when more than a month old. Seeds three weeks old have 
a germination of 50 per cent. 
Cottonwood is fastidious with regard to a suitable germinating 
bed. Reproduction is almost entirely restricted to situations where 
the mineral soil is exposed, and even on such sites the seed demands 
abundant moisture. This explains why cottonwood seldom starts on 
any situations except moist, newly formed sandbars or abandoned 
cultivated fields. 
' Reproduction by seed in the Mississippi bottom lands is probably 
dependent to a considerable degree on the overflows which saturate 
the surface soil. Even on areas not inundated the water table may 
rise so near the surface as to supply the seed with sufficient moisture. 
Reproduction seems to be surest on situations which have been inun- 
dated, and every exceptionally high overflow is followed by a rank 
growth of young cottonwoods wherever the shade and ground cover 
will permit. It is probable that another benefit of this high water 
hes in the thin silt deposit left by the receding water, which affords 
an ideal germinating bed. 
FROM SPROUTS. 
Cottonwood reproduces also from sprouts, both from the stump 
and from the roots. Root sprouts, however, are comparatively infre- 
quent and from the standpoint of management are of minor conse- 
quence. Stump sprouts originate both at the base of the stump and 
the root collar, and at the top of the stump from the cambium be- 
tween the bark and the wood. 
