46 PISTILS AND STAMENS 
paper the drawings in Figure 54 and with lines indicate the parts 
in A from which the different parts shown in B have come. 
In many plants the endosperm does not remain outside of the 
embryo as it does in Corn and other grains. If one removes the 
thin rind-like testa from a soaked Bean, all that remains is the 
large embryo. The endosperm is stored in the embryo and as a 
result the embryo is much enlarged and fills the space within the 
testa. Clover, Alfalfa seed, and many other seeds have the endo- 
sperm stored in the embryo. Study the Clover seed in Figure 55. 
Notice that there is apparently no endosperm, and that the much 
enlarged embryo occupies nearly all the space within the testa. 
In some seeds a stored food known as perisperm occurs. 
Usually as the ovule develops into the seed, the nucellus is de- 
stroyed and replaced by the developing endosperm, leaving only 
the integuments from which the seed coat is formed. However, 
in the formation of a few seeds, some of the nucellus remains, and 
a portion of its outer region becomes filled with stored food, thus 
forming the layer of stored food known as perisperm, which sur- 
rounds the endosperm and embryo. 
Pollination 
Nature of Pollination. — Pollination is the transference of 
pollen to the stigma. After the pollen is on the stigma, it may 
produce a tube reaching to an ovule and effect fertilization, or 
it may lie dormant; but in either case the stigma is considered 
pollinated. Much pollination occurs in nature that does not 
result in fertilization. Corn pollen, for example, as it is blown 
about may fall on the stigmas of various other species of plants, 
but since no fertilization results, the pollination is not effective. 
Pollen is usually effective only on stigmas of plants similar to 
the plant which produced the pollen. Thus Apple pollen is 
effective only on Apple stigmas, Corn pollen only on Corn 
stigmas, etc. 
Pollinating Agents. — The most important pollinating agents 
are gravity, wind, insects, and man. In some cases, as in Rice, 
Wheat, and Oats, where the pollen falls from the anthers to the 
stigma, pollination depends upon gravity. Even in orchards 
some pollination may be accomplished by pollen falling from the 
higher branches. \ In early spring, before there are many insects, 
many of our trees, such as Willows, Poplars, Oaks, and Pines, 
