102 



The Flora of Wiltshire. 



process to the influence of the light alone, the combined action of 

 heat with light not being exerted till the flower has emerged from 

 the water. Again, the mode in which the plant is affected by the 

 operative agent has not been fully or correctly explained. I shall 

 therefore endeavour to show that light and heat acting at first 

 separately, and afterwards conjointly, produce the different stages of 

 elevation, not by primarily affecting the peduncle with the flower, 

 but by acting primarily on the flower alone : the peduncle being 

 affected secondarily, only by means of that vital sympathy which 

 most contiguous organic structures have with each other. 1st. The 

 water beneath which the flower reposes in the early morning, being 

 a bad conductor of caloric in a downward direction, intercepts the 

 transmission of the calorific portion of the solar rays. The light 

 above then in any considerable degree penetrates the translucent 

 fluid, to the flower; and occasions not only the commencement of 

 the motion, but its continuance upwards till the flower emerges 

 above the surface, when its full expansion and further elevation are 

 effected by the combined influence of the heat and light. This ex- 

 planation is rendered more probable from the circumstance that the 

 flower emerges from its watery asylum at an early period in the 

 morning, before the water could have been affected in any consi- 

 derable degree by the solar heat. 2nd. That the ascent of the flower 

 is caused by the action of the peduncle, whose motion results, not 

 from the direct influence of the light upon itself, but by sympathy 

 with the flower which it supports, is also rendered probable from 

 the circumstance that these periodic motions cease, as soon as fer- 

 tilization of the ovules or immature seeds has taken place, at which 

 time the petals wither, and the germen descends to the bottom, 

 there to remain permanently for the ripening of the seeds. Now 

 if the stalk had been in the first instance sensible to the direct ac- 

 tion of the luciferous rays, we might expect such sensibility to con- 

 tinue independent of the state of the floral organs. It would appear 

 therefore that the cessation of motion of the peduncle after impreg- 

 nation, is indicative of its dependance on the organic sensibility of 

 the flower. It can scarcely be said that the elevated germen de- 

 scends finally, in consequence of the loss of the buoyant apparatus 



