22 VEGETABLE ORGANOGRAPHY. 



of a leaf, I have frequently seen, especially in the leaves 

 of Monocotyledons, some cellules which appear perfectly 

 imtouched, separated entirely or in part from their 

 neighbours ; but these facts are so rare, that one cannot 

 but think that they are either out of the ordinary course 

 of things, or that the tissue of neighbouring cellules has 

 perhaps been broken. 



3d. The separation of cellules by boihng in water 

 or in nitric acid, seems likewise to confirm the idea of 

 the double nature of the membranes, and tends to make 

 us consider the cellules as distinct bodies. But it must 

 also be confessed that, in subjects so difficult, it is dan- 

 gerous to decide after observations where the natural 

 tissue has been altered by such powerful agents. The 

 boiling in water itself has all the inconveniences of the 

 maceration formerly made use of — that is to say, it 

 destroys the delicate intermediate organs, and tends to 

 isolate artificially organs which may in reality be con- 

 tinuous in their natural state. 



4th. There are some cases where one sees the cellular 

 tissue resolve itself into isolated bodies, which at first 

 sight appear like dust, and which, viewed through the 

 microscope, evidently appear as cellules : of this kind 

 are the mass of globules which are found in Lenticels 

 vipon the development of adventitious roots, &c. From 

 the general result of these observations, I do not now 

 retain any doubt that the cellules which compose the 

 cellular tissue in general are vesicles distinct from one 

 another and differently joined together. 



If I wished to search in nature for an example of 

 this kind of structure, which, though rude, should be 

 visible to the naked eye, I would cite the membranous 

 vesicles, full of juice, which are found in the interior 

 parenchyma of the orange : each of these little sacs, 

 which I do not pretend to compare completely to the 



