1S4 On the Physiology of Vegetahtes. 



skin is within, the while is without. But in flowers, the pabulum 

 is white, and the upper and under cuticles coloured. To the 

 pabulum the petals of flowers are indebted for their brilliant ap- 

 pearance, and not to the juice uhifh inflates them (which is 

 generally of a dull and livid colour); but the bubbles receiving 

 the rays of the sun, and returning them to the retina through 

 these colours, paint them with a vivid glow impossible to ex- 

 press in words ; but easily shown bv throwing the light of the 

 sun through a small glass bubble on the dullest colour imagi- 

 nable, and it immediately returns the brightest of tints. Thus 

 these bubbles receiving the rays of the sun (which strike each 

 drop of water) are enlivened and enlightened by the reflection and 

 refraction of that bright ray of light seen in every bubble, and 

 striking the retina, by which means the whole flower would be- 

 come a blaze of light too violent for the eyes, had not Nature, 

 to soften it, covered it with a cuticle of a gauze-like texture, 

 which, refracting each rav, gives it a softness and beauty seen 

 only in flowers. This being their form, it must stand to reason, 

 that, in spite of the upper cuticle, much heat mu^t i)e evolved ; 

 and yet it did not occur to me to measure it, till I received a 

 letter from Sir J. E. Smith, in answer to one I wrote to him, re- 

 specting the raising the thermometer during the fructification of 

 the seeds ; when he requested me to see whether the polished 

 surfaces of the petals were not the cause of heat still more than 

 the seeds. This inunediatelv set me to tvork ; — the only trial 

 T have ever seen on the subject was one made by the excellent 

 Mons, Hubert in the island of Bourbon ; but it is given by Mons. 

 St. Vincent in so strange a wav, that I cannot make it out. In 

 the first place he savs that the maximum of the heat was at sun- 

 rise. " That Madame Hubert, who was blind, was much struck 

 by finding the plant Jeel hot to her hand ; and that when the 

 thermometer was applied to the spadixes of the plant, it rose to 

 30° of Reaumur, the standard thermometer being 18'." Now 

 this in Fahrenheit would be 50' and G2°. Now how could Ma- 

 dame's hand, which even supposing her seventy, could not be less 

 than 75^ in that climate, feel 62" hot to her hand ; when it 

 was thirteen degrees cooler than her own flesh, and would there- 

 fore be cold to it ? 



I cannot help thinking that there was so much handling, and 

 cutting, and placing the plant round the instrument, that the 

 hand must have communicated much of the heat it possessed to 

 the vegetable it held. It certainly was neither the corolla nor 

 the seeds that gave it ; since the male and female were cut to 

 pieces and disposed round the thermometer, and all motion must 

 soon have ceased in thus dismembering the plant. However, we 



are 



