160 ELEMENTS OF BOTANY. 
196. Cross-Fertilization and Self- Fertilization. — It was long 
supposed by botanists that the pollen of any perfect flower 
needed only to be placed on the stigma of the same flower to 
insure satisfactory fertilization. But in 1857 and 1858 the 
ereat English naturalist, Charles Darwin, stated that certain 
kinds of flowers were entirely dependent for fertilization on 
the transference of pollen from one plant to another, and he 
and other botanists soon extended the list of such flowers until 
it came to include most of the showy, sweet-scented or other- 
wise conspicuous kinds. It was also shown that probably 
nearly all attractive flowers, even if they can produce some 
seed when self-fertilized, do far better when fertilized with 
pollen from the flowers of another plant. This important fact 
was established by a long series of experiments on the number 
and vitality of seeds produced by a flower when treated with 
its own pollen, or self-fertilized, and when treated with pollen 
from another flower of the same kind, or cross-fertilized.” 
197. Wind-Fertilized Flowers.* — It has already been men- 
tioned (§ 189), that some pollen is dry and powdery, and 
other kinds are more or less sticky. Pollen of the dusty sort 
is light, and therefore adapted to be blown about by the wind. 
Any one who has been much in cornfields after the corn has 
‘“‘tasseled”” has noticed the pale yellow dusty pollen which 
flies about when a cornstalk is jostled, and which collects in 
considerable quantities on the blades of the leaves. Corn is 
moncecious, but fertilization is best accomplished by pollen 
blown from the “tassel” (stamens) of one plant being carried 
to the “silk” (pistils) of another plant. This is well shown 
by the fact, familiar to every observing farmer’s boy, that 
solitary cornstalks, such as often grow very luxuriantly in 
an unused barnyard or similar locality, bear very imperfect 
1 See Darwin’s Cross and Self-Fertilization in the Vegetable Kingdom (especially 
Chapters I and II). 
2 On dispersion of pollen see Kerner and Oliver, vol. II, 129-287. 
3 See Miss Newell’s Botany Reader, Part II, Chapter VII. 
