114 Researches respecting the 



nf which were filled with a red juice, and always with as 

 little effect. 



As I was not able to succeed by these means, I had re- 

 course to injection. I immersed the fresh cut extremity of 

 different leaves, for twenty-four hours, in a decoction of 

 Brasil wood : I then observed them, and found that the li- 

 quid had not penetrated the parenchyme beyond the cut 

 surface. 



I again immersed several fragments of leaves in the same 

 decoction: I dissected them with attention, and observed 

 that the colouring liquor had penetrated beyond the sections 

 into the utricular interstices, that the membranes of the 

 utriculi had been a little covered by them, but that the 

 Utricular juice had retained its natural colour. 



I substituted for this decoction ink and a solution of the 

 acetite of lead, which I precipitated by sulphate of potash, 

 without obtaining from this process a more satisfactory re- 

 sult. I th.-^n placed in a decoction of Brasil wood, under the 

 air pump, large fragments of the leaves of the aloe and of the 

 fritillaria, and of the leaves of the mesembryanthemum and 

 cactus. I exhausted the receiver; and taking the leaves from 

 the liquid, I observed that in the leaves of the aloe the injec- 

 tion had penetrated at the sections only to the depth of an 

 inch ; that the leaves of the fritillaria were almost entirely 

 penetrated by the injection, which in colouring it had given 

 it that transparency which is observed in leaves that have re- 

 mained under water ; that in the cactus and the mesembry- 

 anthemum the injection had not penetrated beyond the cut 

 part . 



Though these injections had succeeded better than the 

 preceding, the result however was the same, since I ob- 

 served that the coloration of the leaves depended only on 

 the liquid introduced into the utricular interstices. 



If we admit that there is a free communication between 

 one utriculus and another, how can we explain the different 

 colours by which the streaked leaves are shaded ? In the 

 spotted orchis, for example, the spots are produced by utri- 

 culi which contain a red juice, while those found between 

 the ribs have a green juice. In the red cabbage the juice 

 •of the exterior utriculi is violet, and that of the interior 

 •ones is transparent. 



These observations inthice me to believe tliat the utricular 



juice does not circulate in the utriculi, but that it is rather 



-slaccnant in them. How, indeed, can we suppose that the 



globules found in so great abundance in this juice, and ti*c 



-prisms met with in most plants, should pass from one utri- 



. . » .., cul'US 



