160 THE REPRODUCTIVE ORGANS 



Many of our forest trees produce similarly reduced flowers. 

 This arrangement, in which the stamens and the pistils are 

 in different flowers but on the same tree, is called monoe- 

 cious (Gr. monos = one, oikos = a house). Such flowers 

 are inconspicuous and unscented, and the staminate 

 flowers produce a large quantity of pollen which is loose, 

 dry, and light, and easily carried by the wind to the large 

 stigmas of the pistillate flowers. In the Willows (Fig. 185) 

 and Poplars (Fig. 186) the two kinds of catkins are borne 

 on different trees, and this arrangement is called dioecious 

 (Gr. di = two). In all such cases the pollen carried to the 



stigma comes from another flower, 

 and when this occurs the flower 

 is said to be cross-pollinated. In 

 Willows the stamens are bright 

 yellow and numerous, and each 

 flower contains a honey-gland or 

 nectary at the base. Insects often 

 visit these catkins and collect from 



Fig. 107. Ripe Stigmas them both hone y and P ollen > with 

 of Mallow curling which their bodies may become 

 among the Anthers. dusted. Thus the pollen may be 



carried to a pistil-bearing catkin 

 and some of it deposited on the stigmas. 



From the abundance of fruits produced by such trees 

 it is obvious that simple and unattractive as the flowers 

 are, they yet contain all that is essential for fruit-produc- 

 tion. Hence stamens and pistil are spoken of as the 

 essential organs of the flower. In the flower of the Stock 

 other parts are present, viz. the sepals, which are protective, 

 and the petals, which are attractive. Both parts are use- 

 ful, but, as we have seen, not essential, for the production 

 of seeds. 



Self-pollinated flowers. In the flower of the Round- 

 leaved Mallow (Fig. 107) there are five free sepals and 



