sentences:  The male catkins are patterned green and brown, long when shedding pollen; the female catkins are green, long at pollination, maturing in early summer to bear 10–20 (50–80) capsules each containing numerous tiny seeds embedded in downy fluff.The fluff assists wind dispersal of the seeds when the capsules split open at maturity.It can be distinguished from the closely related North American "Populus tremuloides" by the leaves being more coarsely toothed.