On the Anatomy of Vegetables. 39 



forms two kinds of different organs 5 the cellular tiffue, and 

 the tubular tiiiue. 



Chap. III. 



Of the Cellular Tiffue. 



This tiffue prefents to the obferver a feries of membranous 

 hags, which on the firit view feem to have no communication 

 with each other. They are not fmall bladders or utriculi, 

 as moft authors affert; they are a membrane, which bends 

 itfelf, in fome meafure, to form vacuities contiguous to each 

 ot>her. In the parts where thefe cells experience no foreign 

 preffure, they are all equally dilated, their tranfverfal and 

 vertical fections prefent hexagons fimilar to the alveolas of 

 bee-hives; each fide of thefe geometrical figures is com- 

 mon to two cells, and the whole tiffue is wonderfully regu- 

 lar: but, when the tiffue is compreffed, the hexagons lofe 

 their fliape, and are converted fometimes into parallelograms 

 more or lefs elongated. The membranous fides of the cells 

 are exceedingly thin and colourlefs : they are tranfparent like 

 glafs, and their organization is fo delicate, that it cannot be 

 perceived even with the help of the moft powerful micro- 

 icopes. They are generally filled with pores, the apertures 

 of which do not certainly exceed the 300th part of a line; 

 thefe pores are bordered with fmall unequal and glandulous 

 rolls, which intercept the light, and refract it with force 

 when they, receive its rays. The cellular tiffue is fpongy, 

 elaltic, and without confidence ; when immerfed in water 

 it becomes altered, and, in a little time, is even deftroyed: 

 it is then reduced to a kind of mucilage. Thefe pores efta- 

 bliffy a communication between one cell and another, and 

 ferve for the transfufion of the juices in that tiffue, which is 

 exceedingly flow. I mud alfo obferve, that it is not a con- 

 ductor of the fluids diffufed throughout the vegetable, and 

 that it produces nothing of itfelf. 



I have faid that the membranes are tranfparent and co- 

 lourlefs : when the tiffue is difengaged from every foreign 

 body, this is true; but it is often marked by colouring fub- 

 (iances, which tarnifh its tranfparency. This tiffue exifts in 

 all vegetables, but not in the fame proportion. Mufhrooms 

 and fuci appeared to me to be compofed only of cellular tif- 

 iue. The bark of monocotyledons and dicotyledons is al- 

 moft entirely formed of it: in thefe, it is generally fomewhat 

 compreffed between the epidermis and the wood; it is filled 

 with refinous juices, commonly coloured green, but fome- 

 times red or yellow, according to the nature of the vegetable. 

 This gives different tints to the epidermis, which is nothing 



C 4 die 



