186 On the Physiology of Fegelalles. 



degree; the seeds gain only 2f ; if indeed it is any thing, the 

 quantity of caloric must be very small, and only at the time of 

 fructification, which may arise from the cjuicker motion of that 

 season ; since it is certain that at no moment the seed is liable 

 to so hasty a revolution, as when the inside of the heart first 

 forms itself. But the heat the cori)lla gives is a decided heat; 

 and it Im to be discovered in every jioxver that will admit the 

 bulb; and I should suppose intended to accelerate the fructifi- 

 cation of the seeds, the completion oi the juice of the pistil, which 

 for the purpose above mentioned may require to be raised to a 

 certain temperature before it is fit to pass down the pistil into 

 the seeds. I always shaded those flowers that were afterwards 

 to be exposed to the sun, till two or three minutes before the 

 experiment began, or probably the heat would have been higher. 

 But it is not certainly owing to the polished surfaces of the pe- 

 tals, for notliing can be less smooth in the microscope: but it 

 is owing to the balls of water that compose the pabulum, which 

 reflects heat from each bubble of water and light ; and if the sun 

 is hot enough to decompose the water (which it certainly does 

 in those petals that have hairs), it of course must reflect great 

 heat from the pabulum; and this may always be increased by 

 taking otf the upper cuticle. But it is not to one sort of form 

 the corolla is confined, though, except tiic Everlasting, the pabu- 

 lums are all formed of bubbles of water. But there are wet pe- 

 tals, such as the hyacinth, which, though they are so filled with 

 liquid, it is (juite wonderful how the skin can keep it from 

 oozing, yet detain the liquid in such a manner as not to wqt the 

 hand on which it reposes. This is really a wonderful thing, and 

 shows in how great a perfection Nature has made these skins, 

 which not only may be so filled with liquor as to be greatly in- 

 flated, but also so thin as to appear perfectly transparent, vet 

 cover the water sufficiently to keep it from too great an evapo- 

 ration, and enough to allow it to decompose water, which the 

 corollas that have hairs certainly do. 



There are still more curious corollas, one sort in particular, 

 which we have so exactly imitated in forming velvet, that it is 

 impossible not to be struck with the similarity of the forn)ation. 

 The upper coloured cuticle is formed of a vessel carried up and 

 down in scollops, and then cut at the top ; — this appears to pro- 

 long the ray of light which falls on it, instead of absorijing or 

 repelling it suddenly, it is thus it acts on feathers, it is this which 

 gives tliem so exquisite a softness. It is this also in miniature- 

 painting which makes a stroke so much softer than a dot. It 

 is this on the cheek of beauty when the soft down shades it, 

 which is so exquisite to behold, and luhich paint so wholly de- 

 stroys. The thick petals, which are mostly flowers belonging 



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