CHAPTER XV 
THE STORAGE OF FOOD-RESERVES—ECONOMIC BOTANY 
Puants differ from animals in many ways. We have 
drawn attention to some. In the matter of the storage of 
food-reserve we have another. Animals rarely store up 
food in their own bodies for future use ; to some extent 
hibernating animals do, and there is the remarkable case 
of the fat-tailed sheep of Thibet which store up fat in their 
tails. Plants, on the other hand, by the very nature of 
their economy, are compelled to make and store up food 
in preparation for periods when a great demand for 
nourishment is made. Most plants have to make pro- 
vision for the formation of flowers and seeds. For this a 
large amount of food-material is required in a very short 
time, and in many plants the whole of their vegetative 
activities seems to be a preparation for this function. 
The annual, for example, accumulates reserves until 
flowering, when a migration of food-material takes place 
from all parts of the plant towards the flowers ; the food- 
material, elaborated by the parent, passes into the seeds, 
and the drain is so exhausting that the plant dies. Her- 
baceous perennials prepare for the winter by storing up 
reserves of food in their perennial parts underground— 
e.g., in bulbs, rhizomes, tubers, etc. When spring comes, 
a current of food-material pours from the seats of storage 
towards the opening buds, and is utilized for the rapid 
growth of the aerial shoots and leaves. Trees also accu- 
mulate great reserves of food. When the buds open in 
the spring, the demand for nourishment is very great, and 
the ascending stream of watery sap, enriched with food- 
material drawn from the stores of reserve, passes into the 
unfolding leaves. 
The most common form of food-reserve is starch. 
The cells of the potato are filled with grains of starch ; 
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