xxn] ANTHOCYANIN 277 



Portula was found growing at the bottom of a deep pool, and 

 entirely free from anthocyanin; but a number of shoots had 

 broken off, by the snapping of the brittle stems, and were 

 floating at the surface, and putting out adventitious roots. In 

 the case of these detached shoots, there was considerable pig- 

 mentation, and some of the leaves were quite red. Again, in an 

 extremely hot sunny summer (August, 1911) in the dykes at 

 Wicken Fen, many young Waterlily leaves of the floating type, 

 which were still rolled and had not reached the surface, were 

 noticed to be brilliantly red. 



The whole subject of anthocyanin has recently been dealt 

 with comprehensively by Miss Wheldale (the Hon. Mrs Huia 

 Onslow) 1 . She puts forward the hypothesis that the pigment 

 arises from a chromogen formed from sugars in the leaf, and 

 that increase in the amount of carbohydrates leads to increased 

 formation of chromogen with the resultant production of antho- 

 cyanin, unless the chromogen be removed. If translocation be 

 slowed down for any reason, such as low temperature, produc- 

 tion of pigment tends to occur. This seems entirely consistent 

 with the facts so far as they relate to water plants. For instance, 

 in the case of the detached shoots of Pep Us mentioned above, 

 there would be little possibility of material being rapidly trans- 

 located from the leaves, because there is nowhere for it to go to ; 

 Miss Wheldale's theory thus explains the relatively high pig- 

 mentation of these shoots. In the case also of the Lemnas and 

 the Podostemads, practically the whole vegetative body con- 

 sists of assimilating organs. The excess sugar cannot, therefore, 

 be removed from those organs, and the theory thus fully explains 

 their liability to coloration. It is also confirmed by the known 

 fact that the Podostemaceae store large quantities of carbo- 

 hydrate, which is used up in their rapid flowering period. In 

 such cases as the Waterlilies, again, the relative coolness of 

 river or lake water may be a hindrance to rapid translocation 

 from leaves to rhizome. As regards the supposed functions 

 of anthocyanin, Miss Wheldale concludes that " For the time 

 1 Wheldale, M. (1916). 



