82 SEEDS AND FRUITS 
tacle; (3) ovary with perianth or bracts forming a husk; (4) ovary 
with calyx forming hairs or spines; and (5) a number of single 
fruits with the modified leaves and floral 
axis of the flower group. A fruit may 
be defined as one or more ripened ovaries 
either with or without closely related 
parts. 
Dissemination of Seeds and Fruits 
Dissemination has to do with the 
scattering of seeds from the parent plant. 
Sometimes the seed is transported naked, 
but often it is transported enclosed in 
the fruit or with some larger part of the 
plant. 
The necessity for dissemination is ob- 
vious, for if the seeds of a plant were to 
Fic. 84.—The dry coiled germinate where formed or on the ground 
fruits (pods) of Alfalfa directly beneath, the resultant conges- 
(Medieago sativa). From tion would prevent the normal develop- 
Farmers’ Bulletin 895, U.S. ment of any of the plants. Green 
Dents ok, penisullne: plants must have sunlight and air, and 
this means that they must have room. 
Of course seeds and fruits are not the only means by which 
plants spread. Many Seed Plants have an additional means in 
either spreading stems or roots which give rise to new plants as 
they spread farther and farther from the parent. The Straw- 
berry depends mainly upon its runners, and the Quack Grass 
much upon its underground stem as a means of spreading. Pop- 
lars, some fruit trees, and Canada Thistle are well known to 
spread by means of sprouts arising from their roots. Most plants 
which do not have seeds spread by means of spores which in some 
cases seem to be a more efficient means than seeds are. For 
example, Wheat Rust, a disease which spreads very rapidly, is 
spread by spores. 
In the dissemination of seeds and fruits, wind, water, and ani- 
mals are the chief agents. In a few plants there are explosive or 
spring-like mechanisms which throw the seeds. 
Seeds and Fruits Carried by Wind. — The wind is one of the 
most important agents in the distribution of fruits and seeds. In 
