RED PIGMENT OF FLOWERING PLANTS. 417 



weather of early spring-, the red-colouring matter of the 

 style, by virtue of its heat-absorbing powers, may materi- 

 ally accelerate the growth of the pollen tube toward the 

 ovary and thus minimise the danger to the pollen grain 

 from exposure on an unprotected stigma. Similarly the 

 red colour of various gymnospermous flowers may ac- 

 celerate their opening. 



The deep red colour assumed in Alpine regions by the 

 flowering spikes of various grasses such as Poa annua may 

 have a similar significance — Kerner suggests indeed that 

 probably the anthocyan converts " light rays " to heat — . 

 We know that a rapid opening of some grasses is brought 

 about by a quick growth of the anther filaments and that 

 this can be effected by placing the grass spike in the 

 mouth. How far this suggestion, that the heat-absorbing 

 anthocyan favours the opening of flowers at the most 

 propitious season, is capable of application to other 

 brightly coloured Alpine flowers must for the present 

 be left undecided ; but, as Stahl remarks, a following 

 up of the question seems likely to bring many interesting 

 facts to light. 



Hitherto plants, of more or less temperate regions only, 

 have been considered and we have seen that in these 

 the anthocyan probably functions as an accessory to chlo- 

 rophyll in the absorption of radiant energy. According 

 to Kerner the energy absorbed is that of the light waves 

 which are converted by the fluorescent colour substance into 

 heat : according to Stahl the heat rays are directly absorbed. 

 The energy so acquired is applied to the accomplishment 

 of the plant's metabolism, especially of the translocatory 

 processes. 



We come next to consider the distribution and function 

 of anthocyan in plants of tropical regions. 



Stahl points out that anthocyan occurs frequently in 

 shade plants of the tropics, chiefly in the under epider- 

 mis, or in the spongy parenchyma of the leaf. In the 

 steaming jungle, where a high temperature uniformly 

 obtains, Stahl sees little need for a means of increase 

 of general metabolism, and consequently casts about to 



