I 82 PLANT RESPONSE 



And I found that many flowers did so in a marked degree. 

 Thus, for example, in two different specimens of Convolvulus^ 

 both full-blown, the flower being subjected to rising tempera- 

 ture, the corolla-bell folded up at exactly 62-5° C. 



We thus see the possibility of obtaining flowers which, 

 having had the same previous history, are likely to exhibit the 

 death- movement more or less at the same point. I thought 

 that such a collection of similar specimens might probably be 

 obtained in a small space, from the capitulum of a composi- 

 taceous flower, and as a matter of fact I succeeded in finding 

 several. The nature of the movement, whether up or down, 

 and its more or less pronounced character, appeared to 

 depend in these cases on the age of the flower. 



In connection with this question, we must remember that 

 in flowers, as in leaves, we may have in a single specimen 

 alternating hyponastic and epinastic growths. It is therefore 

 conceivable that the death-movements of old and young 

 flowers may take place in different directions, and that at 

 some stages there may be little or no motion of any kind. 

 However this may be, I have found that in the double Indian 

 marigold at the temperature of 625° C. the florets arranged 

 themselves in two groups, the outer and lower whorls turn- 

 ing down, and the younger or central whorls rising up, 

 at the critical temperature. In the case of .some of the 

 large garden daisies, yellow and white, I found the critical 

 temperatures to lie between 61-5° C. and 6^° C, the death- 

 movement consisting of a folding up in some cases, and a 

 curving down in others. If the flower have been subjected 

 to uniform illumination on all sides, then the movement of 

 all the florets will take place within a degree or so. In the 

 French marigold, grown in India, the florets of the ray fold 

 up, at from 59° C. to 60° C. From these experiments we 

 see that, the death-point for all the flowers on the same 

 capitulum being about the same, it might be possible to 

 treat one-half of the florets of a single flower-head as normal 

 or standard, while using the rest for comparative study on 

 the influence of various agencies. 



