372 CHLOROPHYLL -GRANULES AND THE SUN'S RAYS. 



other hand, is formed of a porous mass of reticular or scaffold-like strands, which 

 may best be compared to a bath sponge. The holes and meshes of this spongy- 

 colourless ground substance contains a green colouring matter, which is dissolved in 

 an oily material, and clothes the continuous small spaces in the form of a parietal 

 layer. This green colouring matter of the chlorophyll -granules, which has been 

 called chlorophyll, is easily soluble in alcohol, ether, and chloroform. If green 

 leaves are steeped in an alcoholic solution, they become blanched in a short time, 

 and the colouring matter passes entirely into the fluid. The alcohol assumes the 

 beautiful green colour which the leaves formerly possessed, and the previously 

 green leaves are now to be seen floating in the green alcohol. In transmitted light 

 the solution appears a beautiful green; but when observed in reflected light it 

 appears blood-red, and therefore the colouring matter displays a marked fluorescence. 

 If a fatty oil is added to the green-tinted alcohol, and the two are shaken up 

 together, the green colour passes into the added medium, while in the alcohol a 

 yellow substance remains, which has been termed xanthophyll. The chemical 

 composition of chlorophyll is not yet so clearly understood as we could wish. 

 It is asserted that it is possible to obtain chlorophyll in a crystallized form. The 

 crystals obtained form green transparent rhomboids, which, when exposed to the 

 light, slowly decompose again. This chlorophyll behaves like a weak acid; contrary 

 to earlier belief, it is free from iron, but leaves behind almost 2 per cent of ash, 

 consisting of alkalies, magnesia, some calcium, phosphoric and sulphuric acids. The 

 fact that the production of these crystals must be preceded by a series of long- 

 continued operations, together with the fact that chlorophyll is extremely delicate 

 and easily decomposed, always allows us to suppose that the crystals mentioned are 

 only a product of decomposition, and do not belong to that chlorophyll which 

 colours the chlorophyll-granules in living cells. It was previously thought that 

 chlorophyll was a mixture of two colouring matters, viz. a blue and a yellow, until 

 later researches demonstrated that this supposition was unfounded, and that a false 

 impression had been received through observation of the process of decomposition. 

 A characteristic absorption spectrum has been obtained for chlorophyll, which is 

 especially useful in all cases where it is a question of demonstrating the presence 

 of very small quantities of the colouring matter in any parts of the plant. With 

 respect to this it is enough to say that the whole of the violet and blue and the 

 ultra-violet rays are cut off from the spectrum, and that it exhibits seven character- 

 istically distributed absorption-bands. It may be further remarked here that after 

 treating the chlorophyll with hydrochloric acid tiny crystals arise, which have been 

 called hypochlorin. The results of all these researches have thrown but little light 

 upon the part which chlorophyll plays in those processes which commence with the 

 decomposition of the absorbed carbonic acid in the chlorophyll-granules. 



Compared with the size of the whole mass, chlorophyll forms only an extremely 

 small fraction of the granules it colours green, and when it is withdrawn by the 

 addition of alcohol, only the colour and not the size of the granules in question is 

 found to be altered. 



