66 



THE BEGINNINGS OF LIFE. 



of silica and phosphates, always enters into the com- 

 position of the latter. In the calculi there is much 

 mineral matter and a smaller quantity of colloidal ma- 

 terial ; whilst in starch-grains there is a large proportion 



Fig. 42. 



Different kinds of Starch-granules contrasted with Globular Carbonate 

 of Lime. (Rainey.) 

 a-d" . Ordinary forms of potatoe-starch. 

 h, h' . Compound granules of ' tons les mois' starch. 



c. Two carbonate of lime ' calculi' coalescing, from the calcifying 

 shell of an oyster. 



of colloidal material and a small proportion of mineral 

 matter. 



The mode of appearance and the character of the 

 starch-grains which are to be found in the cellular tissue, 

 are best studied by making thin sections of any grow- 

 ing plants in which starch is usually formed in large 

 quantities. Very young potatoe-tubers answer well for 

 this purpose. When submitted to microscopical exami- 

 nation, Mr. Rainey says 1 : — ^In such sections, in this 

 and the majority of plants, the starch-cells in the 



^ See ' Jrnl. Microsc. Science,' i860, p. 2. 



