410 SCIENCE PROGRESS. 



anthocyan occurring in the upper epidermis of many Alpine 

 plants, and which he finds is the more developed the more 

 intense the light, Kerner regards as a protective screen to 

 chlorophyll. 



It is seen then that anthocyan, in its time, plays many 

 parts. The last-mentioned screen theory may be first con- 

 sidered, Kerner supports his view by interesting observa- 

 tions on the growth of plants in Alpine (Tyrol) regions. 

 He finds, for example, that Satureja hortensis flourishes at 

 heights of 2195 metres, and he attributes this to its power 

 of forming large quantities of screening anthocyan. Flax, 

 on the other hand, grows well at 1500 metres, but turns 

 yellow and dies at 2195 metres. Could flax manufacture 

 anthocyan like Satureja, Kerner adds, it would blossom 

 and fruit like it. Kerner attributes the death of the flax 

 to the destruction of its chlorophyll, which, in the case of 

 Satureja, he assumes to be screened by anthocyan. But 

 this inference is hardly justifiable. It is true that Prings- 

 heim (18) showed long ago that intense artificial light 

 destroyed the green - colouring matter of living plants, 

 and indeed in some cases destroyed the protoplasm itself. 

 Wiesner (19) similarly has brought experimental evidence 

 to show that chlorophyll may be destroyed by too intense 

 sunlight. Other observers have expressed themselves in 

 the same sense (20). johow (21), for instance, states his 

 belief that the action of light on chlorophyll is indirect, and 

 takes efl"ect especially in young and in shade-loving members. 

 So that although some writers, such as Stahl (22), do not 

 attach great importance to this destroying action of sunlight, 

 it may be conceded that too intense insolation is a source 

 of danger to the plant. 



This general truth, if general truth it be, is not suffi- 

 cient to make Kerner's interpretation of his results justifi- 

 able. For Pringsheim (23), and in more recent times 

 Marshall Ward {24), have shown that the destructive action 

 of light commences in the region of the blue-green, and rises 

 to a maximum in the violet. Till the precise spectrum of 

 the pigment in Sahweja be examined, it cannot be affirmed 

 that this body is capable of acting as an efficient absorbent 



