AND CROSS-FERTILIZE THEIR 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 food which flowers provide for 
them. The familiar rhymes of Dr. Watts directed the attention of young people 
