114 MINUTE STRUCTURE. [chap. 



full-gro\vn cells. It would appear to be usually an inter- 

 mediate condition of the plant's ternary food, either pre- 

 ceding the formation or immediately following the solution 

 of starch. It abounds in the cell-sap of the stem of the 

 Sugar Cane and of some Palms. 



lo. There is another important cell-content of which we 

 have not spoken. If you take any green part of a plant 

 (and it will be best to take a morsel from some succulent 

 leaf, or the thin leaf of a Moss), and examine the cells under 

 a powerful microscope, you will find that the entire cells 

 are not coloured green, neither are the whole of the cell- 

 contents, but that the colouring matter is limited to very 

 minute granules lying in the colourless fluid contents. 

 These are called the ^/^/^^r^//^'// granules. The development 

 of the green colour of these granules is determined by the 

 action of light, as may be proved by growing plants in total 

 darkness, when they become blanched. The presence, 

 moreover, of a minute quantity of iron is found to be 

 essential to the assumption of the green coloration. The 

 green colour may be easily removed by a little spirits of 

 wine, leaving the granules, which are essentially but simple 

 segregated portions of denser protoplasm, almost unaltered. 

 Upon the presence of the green colouring matter of these 

 granules under the influence of solar light indirectly depends 

 the most characteristic phenomenon of vegetable life — the 

 assimilation of material adapted to vegetable and animal 

 growth from the inorganic binary compounds, carbonic acid 

 and water. 



Ti. Besides starch, oil, and chlorophyll, there may fre- 

 quently be found minute crystals, either in the form of 

 needles, or collected into nodules, lying in the cavity of 

 cells. They are called raphides, and are, generally, of 

 subordinate importance. 



