POLLINATION OF FLOWERS 
675 
Close or Self-pollination .—But while 
there is wide provision for cross-pollina¬ 
tion among flowers, they very generally 
have the power of self-pollination, so that, 
in the event of' the failure of cross-pollina¬ 
tion, before the period of blooming closes 
self-pollination may occur. The more com¬ 
mon ways are as follows: 
a. The stamens lengthen, contract, or 
bend so that the anthers touch, or drop pol¬ 
len on the stigmas. 
b. The pistils lengthen, contract, or bend 
so that the stigmas receive pollen from the 
anthers. 
c. If lobed, the lobes of the stigma roll 
back so that they touch the anthers. 
d. The filaments and styles become twist¬ 
ed together. 
e. The corolla in wilting closes, causing 
the stigmas to be pollinated. 
f. Self-pollination caused by the growth 
or movement of the petals. 
g. Change in the position of the flower 
caused by the curving of the flower-stalk. 
In addition to the many plants in which 
self-pollination occurs in the event of cross- 
pollination failing to occur there are many 
plants which are regularly self-pollinated 
and self-fertilized. When the flowers ex¬ 
pand, the anthers rest directly against the 
stigmas, which thus necessarily receive the 
pollen. Many plants produce, besides con¬ 
spicuous flowers, small green flowers, which 
never open; and which, altho invariably 
self-fertilized, are very fertile (cleisto- 
gainy). Many of these self-fertilized plants 
are very common, very vigorous and fer¬ 
tile, and extend over a large portion of the 
earth, as the ehickweed, shepherd’s purse, 
and doorweed. They prove conclusively 
that, altho nature may abhor perpetual 
self-fertilization, she does not abhor self- 
fertilization. On the contrary, it is a most 
valuable principle which is carefully pre¬ 
served, and upon which the plant world is 
largely dependent. The contrivances, says 
Kerner, to bring about self-fertilization, 
are no less numerous than those which fa¬ 
vor cross-pollination. “That flowers should 
be adapted at different times to two such 
diverse purposes as cross and self pollina¬ 
tion is one of the marvels of floral con- • 
struction.” 
These facts have led certain botanists 
to question Darwin’s conclusions as to the 
evil results of continual self-fertilization, 
and to assert that the good effects of inter¬ 
crossing are only a temporary stimulant 
and are not permanent. In the opinion of 
Henslow, self-fertilized plants are best fit¬ 
ted to survive in the struggle for life. To 
sum up, he says they are very numerous, 
increase very rapidly, are very vigorous, 
flourish in the most neglected ground, and, 
being independent of insects, are best able 
to establish themselvesi in foreign countries, 
and are, therefore, of world-wide distribu¬ 
tion. 
It should, however, be noted that the 
forms which are continually self-fertilized 
are admittedly degraded or retrogressive 
species, or at least not advancing in devel¬ 
opment. Like certain groups of animals 
they are adapted to certain places or con¬ 
ditions in nature where they appear able 
to maintain themselves indefinitely. But 
for races of plants which are rapidly evolv¬ 
ing, cross-fertilization appears to be essen¬ 
tial. Darwin showed that, when the off¬ 
spring of cross-fertilization were brought 
into competition with the offspring of self- 
fertilization, the former always gained the 
mastery and survived. It would, therefore, 
appear that intercrossing in an advancing 
race of plants would be indispensable in 
enabling it to overcome its competitors. 
FLOWER-GROUPS. 
Flowers according to the ways in which 
they are pollinated are divided into three 
groups. 
Flowers pollinafed by the wind (Anemo- 
philae, wind-lovers). 
Flowers pollinated by water (Hydro- 
philae, water-lovers). 
Flowers pollinated by animals (Zoidio- 
philae, animal-lovers). 
Flowers pollinated by animals may again 
be subdivided into: 
Snail-pollinated flowers (Malacophilae). 
Bat-pollinated flowers (Chiropterophi- 
lae). 
Bird-pollinated flowers (Ornithophilae). 
Insect-pollinated flowers (Entomophilae). 
Flowers pollinated by insects are divided 
into: 
Bee-flowers. 
. Bumblebee-flowers. 
