AND CROSS-FERTILIZE TBEIR FLOWERS. 39 



the stigma of the shortest style, — each to each. Not only is the pollen, through 

 such wonderful arrangements, so distributed as to secure cross-fertilization, but 

 the end is further secured by a 



80. Preference of Stigma for Pollen of other Flowers than its own. In dimorphous 

 and trimorphous flowers, such as have just been described, it has been ascertained 

 that if pollen is placed upon the stigma of the same blossom, or even on that of 

 another blossom of the same sort, it takes little or no effect. There are cases 

 where the stigma gets naturally covered with its own-flower pollen without Set- 

 ting seed, but when touched with the pollen of another flower it seeds perfectly. 

 This explains, at length, the remarkable thing (described in paragraph 37) that 

 the blossoms of Peas, Beans, and of Dicentra or Bleeding-heart and the like, 

 generally set little or no seed when insects are excluded, although the parts are 

 so disposed that the stigma must be dusted by the pollen of the stamens enclosed 

 with it. Why even such flowers need the aid of insects is now clear. This pref- 

 erence of pollen for other than its own blossom, however, is strictly 



81. Within the limits of the Species. The pollen which is conveyed to the stigma 

 of a different species is inactive and without result, in all but species that are 

 pretty nearly related, and in many of these. Apple-blossom pollen, for instance, 

 does not fertilize pear-blossoms, and vice versa. Cross-breeding among flowers 

 of the same species is the rule, — among different species the exception. It may 

 be done, however, to a certain extent, but always with more difficulty ; it rarely 

 occurs in nature left to itself. Crossing of species produces Hybrids : by recourse 

 to it gardeners and florists greatly diversify certain flowers and fruits ; for the new 

 sorts produced inherit from both parents : the cultivator aims at originating and 

 preserving those that combine the most desirable qualities of both parents. 



82. Advantage of Perfect Flowers. The greater number of species, and far the 

 greater number of those that are visited by insects, are perfect, that is, with sta- 

 mens and pistil in the same blossom. Yet separated flowers would seem best for 

 the end in view, cross-fertilization in them taking place of necessity. But, with 

 insects to assist, it is better, that is, more economical, to have perfect flowers; 

 for, while the crossing is equally secured, both flowers produce seed. " The econ- 

 omy of Nature " of which we read is something more than a figure of speech. 



83. The reciprocity of flower and flower, and of insects and flowers, is some- 

 thing admirable. Insects pay liberal wages for the fopd which flowers provide for 

 them. The familiar rhymes of Dr. Watts directed the attention of young people 



