



u 



THE CAUSES OF FLUCTUATIONS IN TUKGESCENCE 



corolla,' the margins gradually assumed an orange 



tint, and on the following day th 



flower, although hardly showing any 

 orange throughout. 



signs 



of collapse, was 



of a 



form brownish 



Experiment IX 



A flower of 



Hibiscus in a chloroform -chamber very rapidly 



•llapsed, and 



the same time assumed a deep 



mar 



red colour. Immersion of the 



discoloured petals respectively in dilute 



acid and 



in 



10 per 



solution of caustic 



potash caused them, in the former instance, again to become scarlet ; and 

 to turn first dull blue, then dull green, and finally ochreous. 



in the latter 



j 



Experiment X, 



Two flowers of Ip 



chamber. The deep blue portions of the 



a violet, and the pale rose of the red parts an 



hederacea were placed in a chloroform- 

 Has almost immediately began to acquire 



ochr 



tint. 



The violet of the bi 



areas 



gradually reddened and, at the same time, the texture visibly became moistened 



The corollas ultimately collapsed, the originally red area 

 the originally blue 



being 



now ochreo 



and 



dull red 



rnicea hederacea was set in a moist chloroform- chamber 

 The blue area of the . corolla gradually became first violet and then 



Experiment XL— A flower of Ip 



at 10-31 a.m. 



dull red, and at the same time 



psed 



Experiment XII.— A flower of Ip 



heder 



was set in a moist ammonia- 



which 



7 



chamber. After three* minutes' exposure it had become of a vivid peacock greei 



gradually faded to a pale ochre. 



The changes in colour in the flowers of Ipomcea hederacea under the influence of 

 chloroform are just the reverse of those which normally take place during the expansion 

 but are the same as those attending the withering of the corollas. Whilst in bud the 



are reddish have an ochreous, and those which 



j 





areas which, during full expansion 



are 



deep blue a red colour; and in the fading and faded corollas of the afternoon 



and night a reversion 



to the bud colouring takes place. 



When the dull red faded 



corollas are treated with acids they become vivid rose colour; and, when treated with 

 alkalis, vivid blue and green, passing on into pale yellow. When the flowers are 





bud and in the faded condition, the cell-sap thus evidently contains a relative excess 

 of acid constituents; whilst, when the flower expands under favourable conditions of light, 

 and specially of temperature, these acids are partially neutralised by the manufacture of 

 alkaline products. Stimulation of the functional activities of the tissues in this case gives 



to effects similar to those accompanying it in tissues containing chlorophyll, and 



of tissues in which the cell-sap is 



rise 



of those occurring in the case 



precisely the reverse 



normally red during their fullest development. The brilliant scarlet of the fully expanded 

 corollas of scarlet varieties of Hibiscus rosa-sinensis is replaced in the bud and in the 

 fading condition by a dull red colour, which, especially in the latter case, is very much 

 of the same character as that developed in the expanded corollas under the influence of 

 chloroform. In the case of chlorophyll-containing tissues, and in those in which the cell- 

 sap is of a blue colour when they are most highly developed, stimulation of protoplasmic 

 activity appears to lead to relative alkalinity; and depression or abolition of protoplasmic 

 activity to relative acidity ; whilst, in the case of tissues containing red cell-sap, precisely 

 the reverse is the case. The essential constituents of both red and blue colouring matters 



•. 



