34 FAMILIAR TREES 



Poplars. This little cup occurs in botli staminate and 

 carpellate flowers, springing from the axil of the bract 

 or scale and surrounding either the stamens or the 

 ovary, as the case may be. In both genera the 

 female flower consists of a one-chambered ovary 

 surmounted by a more or less two-lobed stigma, 

 and forming a small capsular fruit, which splits open 

 by the rolling backward and downward from its 

 apex of two valves. This suggests that there are 

 actually two united carpels. 



The fruit contains a number of minute seeds, each 

 enclosed in a tuft of long white hairs springing from 

 its base, from which characteristic these trees have 

 acquired their American name of Cottonwoods. 



The Poplars form, as a rule, larger trees than the 

 Willows, with broad leaves ; their catkins droop, 

 whilst those of Willows are more or less erect ; 

 and their catkin-scales are slashed into several lobes, 

 whilst those of the other genus, though hairy, are not 

 notched. Another and more physiologically interesting 

 difference between the two genera is that, whilst the 

 Willows have two, three, four, five, or even twelve 

 stamens to each flower, and produce honey, so that 

 their flowers are visited by insects, the Poplar 

 blossoms have no honey, depending entirely upon the 

 wind for the dispersal of their pollen, and being 

 obliged to have, in consequence, more stamens, gener- 

 ally from six to twelve, or even thirty, to a flower. 



The name Populus has been supposed to be con- 

 nected with the Greek palpalus, from polio, to quiver, 

 but there is no evidence of any Greek name resem- 

 bling Populus Possibly the mere difference in 



