STARCH. 



55 



70. There are two kinds of starch in every starch grain. 

 The great mass is made up of a more readily soluble form, 

 the granuluse, while the remainder, amounting to not more 

 than from two to six per cent of the whole grain, is less solu- 

 ble, and bears some resemblance to cellulose ; it is distin- 

 guished as starch-cellulose. These two forms are intimately 

 combined throughout the whole starch grain, so that upon 

 the removal of the granulose by solution a perfect skel- 

 eton of the grain still re- 

 mains. 



71. The first forma- 

 tion of starch appears to 

 take place in the chloro- 

 phyll-bodies when they 

 are exposed to the light 

 (Fig. 43, B, p. 52, and 

 Fig. 36, p. 45). The 

 grains thus formed are 

 extremely minute, and of 

 different shapes and sizes 

 in each chlorophyll-body ; 

 they do not remain and 

 grow into larger grains, 

 but are dissolved upon 

 the withdrawal of light. 

 Thus the starch formed 



during the day disappears F 'S: 45.-Cell of endosperm of Indian corn, 

 . c i". containing polygonal starch grains, separated by 



during the nijmt and IS thin plates of protoplasm. In the figures a to g, 

 . , , , , the starch grains, taken from a germinating In- 



dOUDtleSS Carried to Other dian corn grain, are becoming dissolved and 

 , . , , T disintegrated, x 800. After Sachs. 



portions of the plant. 



72. The formation of ordinary starch grains always takes 

 place in protoplasm ; in fact, they may be said to be secre- 

 tions from the protoplasm, just as cellulose is said to be a 

 secretion. In a cell whose cavity is filled with full-grown 

 starch grains the protoplasm has almost entirely disappeared, 

 only small portions of it remaining as thin plates or scales 

 between the grains (Fig. 45). 



(a) Starch occurs in nearly all chlorophyll-bearing plants ; it is absent 

 only in Nostocacece, Oscillatorice, and other algae whose chlorophyll- 



