SALICACE^E. 251 



ament is characteristic of several other families also. The 

 willows are dioecious, the male and female catkins being borne 

 on different plants. The catkins appear like great masses of 

 either stamens or pistils. But if we dissect off several of the 

 flowers from the axis, we find that there are many flowers, each 

 one subtended by a small bract. In the male or "sterile" 

 catkins the flower consists of two to eight stamens, while in the 

 female or ' ' fertile ' ' catkins the flower consists of a single pistil. 

 The poplars and willows make up the willow family. 



Exercise 68. 



408. The willow (Salix discolor). 



The leafy shoot. Determine the arrangement of the leaves of the willow ; 

 sketch a leaf showing its form, the character of the margin, and of the vena- 

 tion. If different willows are at hand compare the color of the twigs, as well 

 as the character of the twigs as to brittleness or litheness. 



The inflorescence. What is the kind of inflorescence? Are both kinds of 

 flowers borne on the same ament (catkin), or on different aments ? 



The staminate catkins. Determine what constitutes a flower by dissect- 

 ing some of them off from the axis of the catkin. What parts of the flower 

 are present ? How many stamens in a flower ? If a hand lens is convenient 

 use it in making out the form of the parfs. Sketch a flower in its position on 

 the axis of the catkin, showing also the bract at the base of the flower. De- 

 scribe the character of the bract as seen under the lens. 



The pistillate catkin. W T hat parts of the flower are present? Compare 

 with the staminate flower. Sketch a pistillate flower with the subtending 

 bract to sliow the form of the ovary, with the divided stigma. Is the pistil 

 sessile or stalked ? How many carpels make up the pistil ? Is there a small 

 gland (nectary) present near the base of the ovary which represents the peri- 

 anth ? Is there a nectary on the staminate flower? 



The fruit. Examine ripe pods of the willow. Determine what parts of 

 the flower unite to form the fruit. What difference between a fruit and seed 

 in the willow ? What means is provided for the dissemination of the seeds ? 



Field observations on the willows. At what time do the catkins of the 

 willow appear? Do they flower before the leaves appear? At time of flow- 

 ering note the character and abundance of the pollen from the stamens. Is it 

 in the form of " dust," or is it adhesive? How are the willows pollinated? 

 Do insects visit the willow flower ? Are willows easily propagated by shoots ? 

 What happens it a willow branch is stuck into damp soils ; when it is left in 

 the water for some time ? 



