76 PLANTS AND MAN 



of the organs resulting from fertilization — the seed. A seed, there- 

 fore, generally consists of a protective coat, an embryo, and stored 

 food either outside the embryo as endosperm, or in the cotyledons 

 of the embryo itself. Just as the sexual generations leading up to 

 fertilization in the apple blossom are invisible, the formation of 

 the seed — hidden within the ovary tissues — is an invisible process 

 also. A familiar seed is the shelled peanut; the brown papery 

 covering is the seed coat, the two halves of the peanut are the 

 cotyledons gorged with reserve food, and the rest of the embryo is 

 almost invisible since the plumule and radicle are tucked in 

 between the prominent cotyledons. Every seed contains within 

 itself an embryo plant in a compact, well protected, and well 

 nourished form; capable of remaining dormant for decades or of 

 germinating as soon as favorable conditions present themselves. 

 It is the culminating triumph of reproduction among land 

 plants. 



Another post-fertilization change which takes place in our 

 apple blossom, as in all flowers, is the formation of the fruit. 

 Because the ovules of a Gymnosperm are borne superficially on 

 cone scales, the seeds have no additional protective structures 

 formed around them. But in the Angiosperm the ovule is buried 

 in the ovary of the pistil; thus the matured ovule, or seed, is from 

 the beginning surrounded by additional tissues capable of protect- 

 ing, or aiding in the dispersal of, the seed. Fruits with few excep- 

 tions always contain seeds and can appear only after production 

 of flowers. So the sequence of events which begins with the pro- 

 duction of a flower and pollination, terminates in the formation of 

 a seed within a fruit. 



The fruit has become an important organ in the life history of 

 a flowering seed-plant; dispersal of the seed is almost as impor- 

 tant as the dispersal of the pollen. Among the Gymnosperms both 

 are taken care of in a primitive way by the wind. Among many 

 Angiosperms fruits have become structurally adapted for more 

 efficient means of wind dispersal as well as dispersal by water, by 

 mechanical devices, and by animals. 



Wind dispersed fruits are generally small, light in weight, and 

 dry (fig. 50) . Some have flattened wings, as in the maple and ash, 

 which aid them in gliding through the air, while others — ^for 



