110 Researches respecting the 



cular interstices, and which reflect the light. To a^r-iire 

 myself of it, I reraovcd the pellicle of a leaf of the 1-ritillaria, 

 and. then cut a piece of pareuchyme, ia which I observed 

 several of these luminous points. J then placed it in the 

 focus of the niiaoscope on a drop of water : by the mere 

 reilcciion of. the light I distinguished ver\' well these points : 

 but \\ hen I observed them transparently they appeared to 

 me opake ; at which I was not surprised, for I had before 

 remarked that globules of air seen ui this manner always 

 assumed that appearance. I gently compressed the paren- 

 chyme to force out the air, which I saw issue in the form of 

 bubbles, and the water having then assumed its place ren- 

 dered the interstices transparent from being opake. 



I have endeavoured to represent the cflect of these lumi- 

 nous points in fig. l ; but I have succeeded only imper- 

 fectly, .since it was necessary to place at the surface of the 

 drawing the luminous points which ought to be in the paren- 

 chyme. 



If the petal of a rose for example, the irregularity of the 

 parenchymatous utriculi of which give rise to large inter- 

 stices, be slightly compressed under water, the an* it con- 

 tains will be iicen to circulate with raplditv, following the 

 ditfercnt iniiections of the interstices. 



1 have already said that the pores communicate with the 

 utricular intei-stices. This will be proved by the following 

 e>periment. 



J subjected to the action of an air-pump the leaves of the 

 gerai/ium pelialmn and of the rinntx sanguineus, which I 

 placed in a vessel lilled with water. On the first stroke of 

 the piston the two surfaces of the leaf w ere covered w ith a 

 dew .^rising from small air bubbles j I then ceased to pump; 

 and re-establishing the communication between the exterioi" 

 air and the receiver, I examined with attention these bub- 

 bles, which I saw decrease and entirely disappear: whence 

 J conclude that tiiis air had returned into the utricular in- 

 terstices by the same way that it issued, that is to say, by 

 the pyres. To convince myself of this, 1 repeated the same 

 experiment on the leaves of the olea flagrans, the upper 

 surface of which is destitute of pores ; and on the first stroke 

 of the piston the inferior surface alone was covered with 

 bubbles,, which re-entered into the leaf in the same manner, 



C. Mirbel reproai;hes Malpighi with having admitted 

 utriculi in tl\e fbnnation of vegetables : he denies the ex- 

 istence of them, and asserts, that instead of utriculi theue 

 is only a cellular tissue, more or less elongated, composed 

 pf Qlie' piocc,. the cells yf wliich are formed by the ceHul^f 



membrane 



