166 Explmmtion of ih". Cuticle of Leaves, 



reason why the birch will grow so much further north than any 

 other tree : its rind is composed of an innumerable quantity of 

 those skins : if it was studded with pores, as all leaves and cuti- _ 

 des were formerly supposed to be, nay, if there were only a few, 

 it would destroy the whole mechanic formation of the leaf: 

 therefore, as soon as the exterior of an evergreen leaf gets 

 pierced by an insect, it decays directly. 



All those grassy leaves of early spring have a peculiar forma- 

 tion : thev receive 710 moisLure, or very Hit le, from the atmo- 

 sphere. The crocus, suow-drop, hyacinth leaf, &e. are all filled • 

 with a glutinous licjuor in their pabulum, whi<-h in a great 

 measure protects them from the early frosts of spring; they have 

 three cuticles above and three below— the upper skin being- 

 ribbed like a grass leaf, and carrying in stripes the spiral wire ; 

 and it is tiie pabulum, which is in pockets, and stands at a great 

 distance, while the cuticles are merely longitudinal vessels, which 

 differ from the gramina only by having a pabulum : they have 

 tiuee cuticles on each side, which are scolloped ; and of course 

 they have no veins, as their place is supplied by the exterior 

 cuticle. Most of the bulbous roots have the thickened juices, 

 luhick are formed to encoimler the difficulties of the early spring, 

 and thus carry in tlieir bulbs a great quantity of nourishment 

 ready prepared. There is a peculiarity in these plants which 

 deserves much study : most of them will shoot without the assist- 

 ance of any earth ; and yet it is evidently not from the quan- 

 tity of nourishment they receive from the atmosphere, (for that 

 is hardly any thing,) but from that which is laid up and accu- 

 mulated in the bulb ; and from some moisture they have the art 

 and mechanism to draw in at the end of the roots, which will 

 always be found wet when growing on a dry floor, or on stones : 

 but this must be a trifling quantity. These bulljous roots, then, 

 form a third means of support to plants, and not the least cu- 

 rious of the three. 



I hope I shall be able to give a more complete picture of the 

 effects of these plants growing without earth, from some trials 

 I am now engaged in. The astonishing difference that may be 

 made in the appearance of bulbous flowers by lessening or in- 

 creasing the nutriment offered, is well known to most gardeners : 

 it requires, however, the nicest viana^^tment : on tlie essential 

 characters it has ?/o powpr; for although, by the multiplication 

 of the petals or other parts, the more consequential organs are 

 destroyed ; yet these changes affect the genera more than the 

 specific distinctions ; and uotwithstanding the number of these 

 artificial varieties, such is the tendency of nature to maintain a 

 uniformity in the mdividuals of the same species, that a neglect 

 of the gardener for a few years will soon bring all these gaudy 



double 



