270 THE FLORIST AND 



cannot be united with it, are not absorbed by the roots. It is as if the 

 roots had a preference for some nourishing substances in the ground, and a 

 dislike for others ; and it is alone by this that we must explain how some 

 substances of the ground are taken up by the plants, and others not ; why, 

 in fine, each plant requires its own soil and is often unable to grow upon 

 other sorts of ground. 



As the plant is fixed in the ground by the roots, so is the stem, with its 

 organs, in relation to the atmosphere. From the different nature of these 

 two situations proceeds a great difference in the development. We have 

 already spoken above of the various forms assumed by the tissue, which we 

 called the tissue of the cells. Among them there is one, of which here, in 

 connection with our present considerations, we must particularly speak. 

 They are, in fact, those cells which are met with on the surface of plants, 

 and which we designate the cuticle. They differ in many respects from all 

 other tissues, though we may believe that they consist of the same types. 

 If the leaf of an Iris be steeped in water during a fortnight, this membrane 

 will become detached from the undermost parts, or the surface may be sepa- 

 rated from the fresh leaf with a sharp knife. We see oblong rhomboidal 

 vesicles, which compose the flat cells of the cuticle. Further, we remark 

 small openings or stomata, which may be compared to the pores in the skin 

 of animals, and formed by two vesicles of a curvate shape, which unite at 

 the end, and leave an open space in the middle. There are also in the 

 membrane two sorts of vesicles, the oblong and the curvate. These open- 

 ings in the cuticle are spread over the whole surface, except in the place of 

 the fibres of the leaf, where they are missing. 



All this is covered by another thin and transparent membrane, which 

 covers the whole cuticle, the openings only excepted, and in which we dis- 

 cover lines, the marks of those which show in the cuticle membrane the 

 tissue of the cells. If a cabbage leaf be steeped in water for some days, 

 this upper membrane can easily be separated. It is caused in all plants by 

 the evaporation of substances which remain in the cuticle in a fixed state. 



It is impossible to enlarge on the subject of this cuticle, which presents 

 itself in innumerable other modifications. This may be said here of the 

 above mentioned stomata, that it may be accepted as certain that they must 

 be in a very near relation to the respiration of the plants, that is, the rela- 

 tion of plants with the atmosphere, chiefly when we consider in what a 

 great quantity they are often found. In the space of []0,001, there are 

 2,846 on an Orange leaf, 1,000 on that of the Purslain plant, 480 on a 



