Starch 



II 



layers. Probably this striated appearance is due to a varying 

 quantity of water in the different parts of the granule. 



The starch substance seems to be separable into two parts, 

 which are allied if not identical in composition, but which 

 differ in properties. The one, known as farinose or starch 

 cellulose, appears to form the skeleton of the granule, and is 

 either stained brown by iodine, or, as in some cases, remains 

 unstained ; whilst the 

 other part, granulose, 

 which forms 94 to 96 

 per cent, of the granule, 

 is coloured blue. 



Granulose is readily 

 soluble in saliva, and is 



thus separated from the -ssm'f— «jl_/(1(!. '\^— ^>si-ji i^«\\ 



skeleton. The same ^S&/S^^^^»^ 



change takes place by 



Fig. g. — Starch Fig. lo. — Cell of endosperm of Zea. Mais, Maize. Thin 



grains from the la- plates of protoplasm separating _ the polygonal starch 



tex of Etiphorhia grains._ a -g, granules from germinating seed of Maize 



splendens. becoming dissolved and disintegrated. (After Sachs.) 



the action of diastase, a substance occurring in germinating 

 seeds, whereby the starch stored up in the seed as a food sup- 

 ply is rendered soluble. 



Starch granules, like those of chlorophyll, require light 

 for their formation ; the quantity needed, however, is greater 

 than that for the production of the green colouring matter. 

 The granules are at first formed within those of the chlorophyll ; 

 then in the dark they are converted into soluble substances 

 which are transferred to other parts of the plant, where they 

 are again fixed as reserve food materials in the form of starch. 



