76 PHARMACEUTICAL BOTANY 
found in or more rarely adhering to the chloroplasts of green 
parts of plants in the form of minute granules. This kind of 
starch is known _as AssIMILATION STARCH. 
Assimilation starch is dissolved during darkness within the 
chloroplasts by the action of a starch-splitting ferment called 
amylase and passes into water-solution as a glucose which is 
conveyed downward to those parts of the plant requiring food. 
In its descent, some of the surplus glucose not used by the cells in 
Fic. 42.—Cell of Pellionia Daveauana, showing reserve starch-grains. The 
black, crescent-shaped body on the end of each grain is the /eucoplast. Greatly 
enlarged. (Gager.) 
their nutrition, is stored up by leucoplasts in medullary-ray cells, 
and in various parts of the xylem, phloem, pith and cortex in the 
form of transitory starch grains. Considerable of it, however, is_ 
carried to the underground parts, such as rhizomes, tubers, 
corms, bulbs or roots, or into aerial storage tissues, as the storage 
cells of seeds, where the leucoplasts store it in the form of larger- 
sized grains called Reserve Starcu. This type of starch is 
generally characteristic for the plant in which it is found. It 
constitutes stored-up food for the plant during that period of the 
year when the vegetative processes are more or less dormant. 
