NON-NITROGENOUS ORGANIC CELL-CONSTITUENTS. 



113 



1. Starch, or amylum (?!(C 6 H 10 O 6 ) or Ci 8 II 30 O 15 ), is almost univers- 

 ally distributed throughout the vegetable kingdom, and is the first evi- 

 dence of the decomposition of C0 2 of the atmosphere by vegetable cells 

 (6 C0 2 -t-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 

 o-ermination in seeds and bulbs, into soluble dextrin and sugar. Under 



Fig. 54.-Starch-Gkantji.es, after Loebisch. 



A, pea-starch; B, rice-starch ; C. oat-starch ; D, wheat-starch : E. »ea«-rtarch; r ; millet-^rch ; O. ^corn-starch ; H, rve- 

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



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 m 

 potato-starch (Fig. 54). 



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

 granules from different sources is given. Microscopic examination ot 



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