282 A TEXTBOOK OF GENERAL BOTANY 
SEED DISPERSAL 
We have seen that the seed consists of an embryo, stored 
food material, and a protective covering. The embryo is ca- 

Fic. 271. Capsule of an orchid 
(Cymbidium finlaysonianum)open 
and with minute seeds being 
scattered by the wind. (x 4) 
pable of growing into a plant, and 
the stored food material furnishes 
it with a supply of food for its 
growth in the period before it has 
become established. Most seeds are 
also provided with some means of 
dispersal. Without this the great 
majority of seeds would fall under 
the parent plant and not be carried 
to a location favorable to germi- 
nation and growth. The mecha- 
nism of dissemination may be a 
part of the seed itself or may belong 
to surrounding portions of the fruit. 
The principal agencies by which 
seeds are dispersed are wind, water, 
animals, and explosive mechanisms. 
Dispersal by wind. Either the whole fruit or the individual 
seeds may be suited to dispersal by wind. Seeds that are thus 
disseminated are characteristically 
light. The means of adaptation to 
wind dispersal may be grouped under £ S 
the headings of minute seeds, feathery 
appendages, flattened fruits or seeds, 
winglike outgrowths, and the so-called 
censer mechanisms. 

Fig.272. Flattened wing fruit 
Minute seeds. The seeds of orchids of Tepminalia calamansanay. 
are very small and, besides, have a light, (x4) 
inflated outer covering. These dust- 
like seeds can be blown by the wind for great distances (Fig. 271). 
Wings. In many cases seeds, and in others whole fruits, are 
flattened or have winglike outgrowths (Figs. 272, 273), or they 
