292 Mr Philip Sewell on the [sess. i.n. 



(b) There is the (usually slow) change during the life of the 

 plant, completed in one day in certain species, especially 

 those of tropical regions. In such cases the elaboration 

 of coloured product is undoubtedly accelerated by heat or 

 climatal conditions, which may, however, have given a 

 character to the protoplasm which is inherited. In summer 

 too, in temperate regions, when it is not uncommon for 

 flowers to last more than a single day, it is not surprising 

 if colour-change is rapid. Thus, we have such flowers as 

 Convolvulus minor and Hibiscus mufabilis, which change from 

 white through rose to red in less than twelve hours ; so 

 also Oenothera and Gladiolus versicolor. In two or three 

 days Lantana, Chciranthus, Cobcca, change similarly — others 

 again still more slowly. Or this change may be partial, as 

 in the spots on the petals of Arncbia cchioides. 



(c) Then we may distinguish the slow or the more quick 

 change just preceding the death of the flower, as in Weigelia 

 and Crcitceijus. This, which is perhaps the most marked 

 colour-change to exhibit itself, is not the change of decay, 

 which is one to brown amorphous masses; it illustrates the 

 regular series of coloured products which under definite 

 conditions are produced from tlie proteids of the cells. Such 

 a change as that from wliite to red in Weigelia or Cratmgus 

 well accounts for the origin of the red varieties of these 

 plants. 



These colour-chnnges in single plants show us in the most 

 extreme manner the possibilities of variation when there is 

 but slight difference in the influences at work ujion, and the 

 conditions of, the cell-contents. Colour-cliange, less evidently 

 from the same causes, yet essentially of the same nature, is 

 also seen amongst the different individuals produced from 

 seed in certain species, e.g., s])ecies of Anemione, Folygala, 

 Aruigallis, &c., especially jjerliajts among annuals. It is 

 evident tliat wherever mere conditions of environment do 

 not produce these clianges we have to loolc for a deeper 

 cause in iidierited charactei-. It may 1)0 that some more 

 suljtle character than any we can yet distinguisli is imparted 

 to the different ovules of the same parent with its ever- 

 varying protoplasm ; and it is essential to reinend^er how 

 great this variation is, for it is sliown, not less l)y flowers 

 changing colour in a single diiy, than by the occasional pro- 



