506 BOTANY OF THE LIVING PLANT 



illustrate their very simple floral structure. In the large shrubby Goat- Willow 

 (Salix caprea, L.) the flowers appear grouped to form the well-known Catkins, 

 or " Palms." These are of two sorts, distributed on different plants (dioecious] 



a b 



FIG. 408. 

 Catkins of the Willow, a, male ; b, female. (After Figuier.) 



(Fig. 408). The male catkins appear bright yellow when in bloom, from 

 their projecting stamens ; the female catkins are more slender, and of olive- 

 green colour. In each case the catkin is a spike. Its main axis bears 



darkly-coloured bracts, and in the axil of 

 each of these is a single very simply- 

 constructed flower. 



The male flower (Fig. 409, a) consists of 

 two stamens, each with a long filament, 

 which bears the anther, with sticky, not 

 dusty pollen. There is no perianth, nor 

 gynoecium ; but on the side next the 

 stem is a nectary, which secretes honey 

 freely at flowering (Fig. 410, A, d}. Other 

 species may have three, four, or more 

 stamens, but no other floral parts (Fig. 

 410, C). The female flower (Fig. 400, b) 

 IS also axillary. It consists only of a 

 gynoecium of two carpels joined by their 

 margins to form a unilocular, superior 

 ovary with two-lobed stigma. The ovules are numerous, and the placenta- 

 tion parietal. A honey-gland is present here also between the flower and 

 the main axis (Fig. 411, A). 



Pollination . The flowers of both catkins are visited freely by insects, both 

 bees and moths, for honey or for pollen. Self-pollination is obviously im- 

 possible, for the plants are dioecious ; but crossing follows as a natural 



a b 



FIG. 409. 

 Flowers of Willow (Salix alba), a, male 



