Chap, ii.] VEGETAL NUTEITION. 97 



If we attentively regard the undulatory amplitude of the 

 luminous rays suitable for making the chlorophyll operate, we 

 see that those active rays have as highest limit O^jOOOSSSG, and 

 as lowest limit O^.OOOSQgeS. They are rays feebly refrangible.^ 



The rays most strongly refrangible, the blue and the violet, 

 as well as the ultra-violet invisible rays, influence especially the 

 rapidity of growth, the movements of the protoplasm and of the 

 zoospores, and so on. 



"We have recently compared, in passing, chlorophyll and the 

 hsematoglobuline of the blood. The parallel is so curious that we 

 must consecrate a few lines to it. 



Chlorophyll and hsematoglobuline are both quaternary sub- 

 stances. They both exercise an elective action on a mineral gas. 



They both are habitually moulded into globules, without 

 nucleus. 



The special property, however, which characterises them 

 seems in both to be independent of the form which they assume. 

 We have seen that a solution of hsematoglobuline absorbs oxygen, 

 and that amorphous chlorophyll, dissolved in the cellular proto- 

 plasm of certain plants, continues, nevertheless, to absorb 

 molecules of carbon. 



Chlorophyll and hsematoglobuline equally seem to form only 

 a temporary association with the mineral element which with 

 special avidity they seek. In effect, the sanguineous globules 

 yield to the anatomical elements of animals their provision of 

 oxygen almost as soon as they have taken it, and, in return, they 

 charge themselves greedily with carbonic acid, thus holding 

 kinship with the chlorophyllian globules in this aspect of their 

 physiology. 



Chlorophyll, though absorbing, like every living substance, the 

 quantity of oxygen necessary to its nutritive movement, does not 

 seem to have a great affinity for that gas. It is probable that 

 in the night it ceases purely and simply to exercise its special 

 action without assuming another ; but it is certain that it does 



' J. Sachs, Traiti de Sotamiqiie, p. 878. 



H 



