THE WALLFLOWER 



35 



tion just described is known as assimilation, or, more 

 accurately, as car&cw-assimilation, for the former term is 

 sometimes used in a wider sense. To this process the 

 formation of all organic substances whatsoever is ulti- 

 mately due, and carbon-assimilation by green plants 

 may thus be fairly regarded as the most fundamentally 

 important of all physiological processes. The assimi- 

 lation of carbon is not really so simple a matter as 

 might appear from the rough sketch just given ; we 

 shall return to the subject later on, when we come to 

 the special consideration of physiological questions 

 (see Chapter III.). 



|8. Starch Granules 



Another important body very generally, though not 

 always, found in the cell-contents is starch. Starch 

 contains the three 



A C 



elements, carbon, 

 hydrogen, and oxygen, 

 in the proportion 

 C G H 10 5 . It occurs 

 in the form of granules, 

 which are easily identi- 

 fied, under the micro- 

 scope on treating with 

 iodine, which gives 

 them a deep blue 

 colour. The larger 

 granules show stratifi- 



Fio. 15. Starch granules, and leuco- 

 plastids. A, From an orchid (PJcajus), 

 large granule, showing stratification : 

 I, the lencoplastid ; c, proteid crystal- 

 loid ; the hilum is at the opposite 

 side of the granule, near the letter A. 

 B, Very young granule, still much 

 smaller than the leucoplastid. 0, 

 Intermediate stage. (After Stras- 

 burger.) Magnified 540 times. 



cation (see Fig. 15, 



A and C) ; that is to say, the substance of the granule 



is made up of a number of successive layers, which 



