THE METABOLISM OF PLANTS. 



153 



mann has shewn, by an extremely ingenious method, that 

 isolated chlorophyll-corpuscles continue for a long time to 

 exhale oxygen. 



We will now study the structure of a chlorophyll-corpuscle. 

 If a cell containing chlorophyll-corpuscles be treated with 

 alcohol, it will be seen that the corpuscles soon lose their 

 green colour; the chlorophyll is in fact dissolved out of them 

 by the alcohol. There remains a colourless corpuscle which 

 gives the reactions of proteid substance, and is, doubtless, of a 

 protoplasmic nature. As regards the mode in which the 

 chlorophyll and the protoplasm are connected together, our 

 only information is afforded by the observations of Pringsheim. 

 He has found that if chlorophyll-corpuscles be treated with 

 dilute acids or be exposed to the action of steam, the chloro- 



FlG. 22 (after Pringsheim). Cell from a leaf of Vallisneria spiralis which had 

 been macerated in dilute hydrochloric acid for six days, and then exposed for 

 some hours to the action of steam. The chlorophyll of the corpuscles has 

 collected into drops at the surface, leaving the corpuscles colourless. The 

 corpuscles are seen to present a spongy or porous structure. 



phyll will exude from the corpuscles in viscid drops, leaving 

 the corpuscles colourless. A colourless corpuscle obtained in 

 this way presents a spongy or trabecular structure, the now 

 empty spaces between the trabeculse having been previously 

 occupied by the chlorophyll (Fig. 22). We learn from this that 

 the chlorophyll is not actually combined with the protoplasm, 

 but that it is retained mechanically within it ; and further, that 

 the chlorophyll is in solution, most probably in some kind of oil. 



