494 



BOTANY 



The family contains only the two genera, Salix, Willow, and Populus, Poplar. 



The flowers of the Willow (Fig. 439), unlike those of all the other Amentaceae, 

 are pollinated by insects, not by the wind. They are accordingly provided with 

 nectaries (the disc-scales) as a means of enticement, and the male flowers have an 

 attractive odour, bright-coloured anthers, and a sticky pollen. Male and female 

 catkins have essentially the same structure ; they are beset with scale-like, entire 

 bracts, in the axils of which the flowers are borne singly. Each male flower possesses 

 usually two stamens (Salix alba), rarely three or more (Salix triandra, S. pentandra). 

 The fruit is a two-valved capsule. The numerous seeds are disseminated by the 



Fiq. 441. — Fagus silvatica. 1, Flowering branch ; 2, a male flower ; 3, a female flower cut through 

 longitudinally ; 4, transverse section of ovary ; 5, cupule and fruits ; 6, fruit. (After Wossidlo.) 



wind ; by means of their hairy appendages they are able to float for a long time 

 in the air. 



The Poplars (Fig. 440) are anemophilous. The flowers, accordingly, are desti- 

 tute of nectaries, which are represented by a cup -shaped disc. The catkins 

 are similar to those of the Willow, but with toothed or lobed bracts. The fruit 

 and seeds are like those of the Willow. 



Geographical Distribution. — The Salicaceae inhabit almost exclusively the 

 temperate and colder zones, where they are often abundantly represented, consti- 

 tuting an important part of the vegetation. They are especially characteristic of 

 the low ground along the banks of streams, where the more shrubby Willows 

 (S. purpurea, triandra, viminalis, etc.) form thicket-like growths, often overtopped 

 by arborescent species (S. alba, fragilis). The Weeping Willow (S. babylonica) is 

 indigenous to the East. 



