Ch. VI, 



METHODS OP CROSS-POLLINATION 



289 



which are these : first, they are inconspicuous, for they 

 lack colored corolla, odor, and nectar, such prominence as 

 they possess being due simply to their abundance, or to the 

 yellow color of their anthers. Second, the male blossoms 

 far exceed in number the female, in obvious correlation with 

 the wastefulness of this method. Third, the stigmas are 

 large, often branching-feathery, thus spreading a greater net 

 for the drifting pollen. Fourth, the flowers are borne in 

 ways to insure free passage of the poUen without inter- 



FiG. 201. — Dimorphic iiowers of Primrose : X 2. 

 Pollen from the upper stamens will develop on an upper stigma, and from 

 lower stamens on a lower stigma, but not other ways. (From Bailey.) 



ference by presence of leaves. Thus the flowers unfold 

 before the foliage in the spring, as with most of our trees, 

 or else they are lifted beyond or above the leaves, as with 

 Pines and Grasses. Fifth, the pollen is found, on micro- 

 scopical examination, to be light in weight and to spread large 

 surface, which is even increased, as in Pines, bj' extension 

 into large empt}' bladders (Fig. 198). Sixth, the stamens and 

 pistils are commonlj^ borne in separate flowers, often upon 

 different plants, thus preventing close- and insuring cross- 

 pollination. While these characters are typical in wind- 

 pollinated flowers, they are not invariable ; for wind-polli- 



