NON-NITBOGENOUS OEGANIC CELL-CONSTITUENTS. 



113 



1. Starch, or amylum (??(C 6 H 10 O 6 ) or CmllaoOjg), is almost univers- 

 al^ distributed throughout the vegetable kingdom, and is the first evi- 

 dence of the decomposition of CO 2 of the atmosphere by vegetable cells 

 (6 CO 3 -{-5 H 2 O = C 6 H 10 O 6 -|-12 0). It is particularly abundant in the 

 cereals, in seeds of the leguminous plants, and in the potato, and in cer- 

 tain roots, tubers, soft stems, and seeds. It forms rounded masses which 

 lie in the plasma of the plant-cells, becoming converted, in the process of 

 germination in seeds and bulbs, into soluble dextrin and sugar. Under 



FIG. 54. STARCH-GRANULES, AFTER LOEBISCH. 



A, pea-starch ; B, rice-starch ; C. oat-starch ; D, wheat-starch : E, bean-starch : F, millet-starch ; G, corn-starch ; H, rye- 

 starch ; I, lentil-starch ; K, potato-starch ; L, buckwheat-starch ; M, barley -starch. 



microscopic examination starch appears as rounded, glistening granules 

 composed of a series of concentric rings. These granules vary in appear- 

 ance and size according to their source. In size they may vary from 

 0.004 mm. in diameter, as when found in beet-seeds, to 0.16 mm., as in 

 potato-starch (Fig. 54). 



In the following table (after Karmarsch) the diameter of the starch- 

 granules from different sources is given. Microscopic examination of 



8 



