FORMATION OF THE WINTER LEAF BTJD. gC^ 



% hardly know a more admirable spectacle in the microscope; 

 it requires but trifling powers to show it well. 



The last process, and completion of the leaf, is the form- Formation of 

 ing of the pores. Whether it is, that the young leaf being the P ore *« 

 thicker and more hairy than it is afterward, the pores are ob- 

 scured and hidden, or that the upper net grows last, I can-* 

 not say ; but in the many hundred forming leaves I have ex-^ 

 posed to the solar microscope, £ have never once been able to 

 view the pores, as I have often done after the leaves had com- 

 pletely quitted the bud. I must not forget to mention, that tv s0;ts ^ 

 there are two sorts of pores in the leaf; the large ones are them, 

 those which receive the dew drops and rain, the smaller are 

 those which appear in the day to give out the oxigen, and at 

 night to inhale the carbonic gas. I mentioned, that I sus- 

 pected these smaller pores of yielding a sort of insensible 

 perspiration ; as 1 find, when out of doors, a scurf only to 

 be seen with a microscope ; and under a glass this seems to 

 rise as water, to bedew the glass. But to place an object in Unnatural si- 



an unnatural situation, in order to judge of its secretions, is tuations may 



, . . . . occasion un- 



sometbmghke putting a human being into a warm bath, to natural' secre* 



judge how fast the blood flows. We know not what un- tions. 



natural secretions we may .cause in that confined air, or how 



much it may alter the nature of the plant, as I shall show at 



a future ti > e with respect to melons and grapes. | 



The two cuticles of leaves differ in most plants: for in Upper and mv. 



the under one I have hardly ever found the large pores into <ler cuticle « 



which t e dew or rain enters ; and but little oxigen is given 



out also from the under part of most leaves ; while this part 



ha*s a number of very small apertures, formed 1 suppose for 



the reception of the carbonic gas. 



I cannot but notice here how strange is thecontradictoryac- Contradiction 



count of the leaves now generally received. They are sup- J^|. ieieceiv 



posed to persp : re 17 fines more than a man : water must 



therefore be yielded from each pore. They at the same tii»e 



give out oxigen, end receive carbonic gas. Is tins credible, 



pr is it not contradictory ? That they give out oxigen in the 



day, and inhale carbonic gas in the night* I am convinced, 



and I think it requires but the simple experiment of 



keeping a plant in the window, and examining it with a 



microscope 8 or 10 timet in a day, to convince a person, that 



there 



