President's Address. 349 



by the reagents used. This, however, is not the case. The 

 constant association of hypochlorin and colouring matter, and the 

 difficulty of separating them, would suggest, as has been already 

 hinted, a genetic connection between them. Xothing positive 

 about this is as yet knowTi. Hypochlorin exists always and only 

 in chlorophyll-corpuscles, because it is a product of these and of the 

 function of their colouring matter, as its formation in light depends 

 on the presence of the colouring matter. Their analogous circum- 

 stances of origin are very striking, especially their formation in the 

 dark in gymnosperms, seeing that both are otherwise dependent on 

 light. Possibly a common origin may be assumed for both in 

 gymnosperms. If a connection between them were established, and 

 the chlorophyll colouring matter was developed from the hypo- 

 chlorin, it would then have to be considered an assimilation product. 

 This is by no means inconceivable. The grounds upon which one 

 denies the possibility of chlorophyll colouring matter arising in 

 consequence of assimilation are no argument against it. That 

 chlorophyll colouring matter is a preliminary condition of assimila- 

 tion has been already refuted and its true function proved. The 

 development of the green colour of gymnosperms in darkness, and 

 the formation of chlorophyll in an atmosphere free of carbonic acid, 

 are as little opposed to it as to the view that hypochlorin is a 

 product of assimilation. That development of green colour precedes 

 assimilation has been shown to be founded on a misinterpretation 

 of appearances. Taking all these facts together, one can hardly 

 shake off the impression that the development of green colouring 

 matter is one of the immediate effects of assimilation. The exact 

 time of development of green colour coincides very nearly with 

 that of the first evolution of oxygen from the tissues, yet after the 

 facts brought forward assimilation must always precede the evident 

 evolution of oxygen. Where light falls on a plant hypochlorin and 

 chlorophyll arise together. According to the theory of the function 

 of chlorophyll now advanced, the green colour of plants is a natural 

 adaptation to the needs of assimilation, and the origin of a i^rotecting 

 screen of colouring matter from hypochlorin, the accumulation of 

 ■which in light is one of the advantageous results of assimilation, would 

 appear to satisfy these needs in a simple and appropriate manner. 



