TISSUES FOR SYNTHESIS 135 



starch. A bud appears upon the surface of the leuco- 

 plast, and the soluble starch is deposited in successive 

 layers around this bud. The starch grain increases 

 in size, becoming larger than the leucoplast and may 

 finally be detached from the latter. Certain mark- 

 ings upon the starch grain have direct connection 

 with the processes of formation. The first part of 

 the starch grain to be produced is termed the hilum 

 and is often of characteristic form. The different 

 layers deposited around the hilum are often apparent 

 through the presence of striations or markings upon 

 the face of the grain. One or several starch grains 

 may be developed from one leucoplast, thus giving 

 rise to simple and corn-pound forms. Several types 

 of starch grains are illustrated in Plate 51. 



Inulin, instead of reserve starch, is formed from 

 the soluble starch or carbohydrate in a few families 

 of plants. Inulin is a reserve material and is probably 

 merely deposited in the cells, the leucoplasts taking 

 no part in the process. 



Sugars. — The formation of sucrose or cane sugar 

 from the soluble starch or glucose takes place in the 

 stems of sugar cane and the roots of the sugar beet. 

 Sucrose is a reserve material and is merely crystallized 

 from the cell sap of the cells in which it occurs. 



Aleurone. — Little information is available on the 

 formation of the albuminous or nitrogenized nutrients 

 of plants. They are possibly formed by interaction 

 between the soluble carbohydrates produced in the 

 leaves and the soluble inorganic salts absorbed through 

 the root hairs. This synthesis may be carried out 

 in the leaf cells and in the meristematic regions of 

 the plant. Aleurone is a nitrogenized reserve material 



