40 INTRODUCTION TO BOTANY 
Often green plants make more food than they use at the 
time, and this surplus food may be stored or reserved in some 
way. Stored food may or may not be used later by the plant, 
and may oftentimes become the food of other plants, of ani- 
mals, or of men. 
38. Food transported by the plant. In all except the sim- 
plest plants the reserve food is carried from the cells in which 
it was manufactured, into other cells. In plants with fleshy 
leaves, like the houseleek, the century plant, the common purs- 
lane, and many others, the greater 
part of the stored starch and other 
nutritive materials has only been car- 
ried to the leaf interior from the outer 
portions of the leaf, where photosyn- 
thesis and other manufacturing proc- 
esses go on. The distance traversed 
may be only a small fraction of an 
inch, but in case much of the food is 
stored in underground parts of the 
Fa. 5. Sachem soon, PaaS it may have been carried for 
Stoel of ean long distances — in large trees, some- 
Magnified 300 diameters times more than a hundred feet before 
it reaches the root at all. 
39. Form in which food is transported. As already stated, 
one of the products of photosynthesis in most plants is starch. 
This is deposited in or about the chloroplasts, during their 
exposure to daylight, in very minute grains. In the course 
of the night these disappear, so that testing a leaf with 
iodine! shortly before daylight usually gives no result. A 
leaf cut off from the stem before nightfall, however, responds 
readily to the iodine test for starch in the morning. This, of 
course, shows that the starch made during the day remained 
in the leaf cells, where it was formed. It is very generally 
true that starch carried from any part of the plant to an- 
other part is first changed to sugar and travels in the form 
1 This turns starch grains blue or almost black. 
