PLANT ORGANS AND ORGANISMS 
199 
The Stigma. —This is usually a viscid papillose surface of greater or 
less expanse functioning for pollen reception. In wind-pollinated 
flowers such as the grasses, the stigmas are the numerous feathery 
hairs which cover the ends of the styles and intended to catch flying 
pollen grains. In animal-pollinated flowers, the stigmas are usually 
small restricted knobs, lines or depressions. The stigmatic papillae 
vary in size in different plants and even may vary on different 
individuals of the same species. Thus in the long styles of Primula , 
the stigmatic papillae are elongated columnar hair-like structures, 
whereas in the short styles of short-styled flowers the papillae are 
small knob-like cellular swellings. 
POLLINATION 
Pollination is the transfer of pollen from anther to stigma and 
the consequent germination thereon. It is a necessary step to 
fertilization. 
When the pollen is transferred to the stigma of its own flower the 
process is called Close or Self-pollination ; if to a stigma of another 
flower, Cross-pollination. If fertilization follows, these processes are 
termed respectively, Close or Self-fertilization and Cross-fertilization. 
Close-fertilization means in time ruination to the race and happily is 
prevented in many cases by (a) the stamens and pistils standing in 
extraordinary relation to each other, ( b ) by the anthers and pistils 
maturing at different times, ( c ) by the pollen in many cases germin¬ 
ating better on the stigma of another flower than its own. 
The agents which are responsible for cross-pollination are the 
wind, insects, water currents, small animals, and man. 
Wind-pollinated, flowering plants are called Anemophilous ; their 
pollen is dry and powdery, flowers inconspicuous and inodorous, as 
in the Pines, Wheat, Walnut, Hop, etc. 
Insect-pollinated plants are called Entomophilous. These, being 
dependent upon the visits of insects for fertilization, possess bril¬ 
liantly colored corollas, have fragrant odors, and secrete nectar, a 
sweet liquid very attractive to insects, which are adapted to this work 
through the possession of a pollen-carrying apparatus. Example: 
Orchids. 
