METABOLISM IN LIVING PLANTS. 



459 



hydrate at certain points in the interior of its substance as well as at its periphery, 

 in addition to another carbohydrate, the so-called granulose. Cellulose and granu- 

 lose, very intimately intermixed, appear in the form of grains, and the mixture is 

 called starch or amylum. Starch-grains are among the commonest of cell-contents. 

 They appear regularly in chlorophyll-bodies and are conveyed from the places where 

 they are first formed to all parts of the plant. This of course is only effected by 



Fig. 121 — Various Forms of Starcli-grains. 



' From tlie seeds of the Com-coclcle {Agrostemma Githago). 2 From a grain of Wheat. 8 From Spurge. * From a Beau seed. 

 ^ From a grain of Maize. ^ From the root-stociv of Catma. 7 From a Potato-tuber (inclosed in cells). ^ From a Potato- 

 tuber (isolated and very highly magnified). ^ From a grain of Oats. 10 From the seed of Lolium temulentuin. n From 

 the corm of the Meadow Saffron (Colckicum autumnale). 12 From a grain of Rice. i3 From a grain of Millet. All highly 

 magnified. 



the solid starch bodies being made fluid, as often as they pass from one cell to 

 another, by the help of an accessory substance, called diastase, which has yet to be 

 described. In many tissues the starch-grains become so accumulated that the cells 

 appear to be crammed with them (see fig. 124 ''). Starch is one of the most important 

 of reserve materials, i.e. of those materials which are not consumed immediately 

 after their formation, but are put away for a time in store-rooms or reservoirs, and 

 then consumed as required in the places needing them. For example, they may 



