4 On the Nourishment produced to the Plant by its Leaves. 



who cannot or will not take the trouble to make use of their 

 eves, that all vegetables must be co\erecl with an impcrvioui 

 skin; since without this no such ([uantitv of oxvgen gas could 

 be retained within the cuticle ; and without this protection most 

 leaves would evaporate all their moisture in one single hot day. 

 In the grassy leaves cf early spring flowers, I gave an example 

 of those leaves which are wholly supported and fed bv their in- 

 terior matter laid up for them in their bulbous roots, and re- 

 quiring from the time of being taken out of the ground neither 

 earth, uater, or rain, (at least very little of the latter,) rill after 

 flowering they are replaced in the earth to receive and form the 

 seeds and flowers of ihe next year; as bulbs will not continue 

 bearing or forming seed or flower except they are rep!;iced hi 

 the earth to rentiv the seeds ; while the rock ]Jants, wholly dif- 

 ferent, are fed by the cuticles of their leaves alone, and deprived 

 of most cf the impervious ones which in all other plant'^ shut out 

 moisture ; t'.ese receive rain and dew from a variety of pores 

 with which tiie excrescences on their leaves are filed, and which 

 form nourishiuent enough eve?i to iiistain very large plants. 



Having now given a sketch of tlie preceding letter, I shall turn 

 to the subject of the present; which will desciibe the maimer in 

 which sand plants are fed ; also how the parasite tribe receive 

 their novrishmevt ; nor shall I leave cut those Ipaves which flower 

 in the leaf, as most admirably drawing the line between those 

 parts requisite to form the flower, or those adapted to the leaf 

 only. I shall then give the description of the cuticle of wet 

 plants, and finish by detailing the changes operated on plants 

 from soil and situation, moisture and dryness, with a few other 

 matters appertaining to the subject. 



The real sand plant very fretjuently possesses a black, dry, and 

 shrivelled root, which sends up but little nourishment except at 

 its first shooting : when it is an annual, it is often discovered 

 with its root half decayed, as if having conveyed the seeds to 

 this their proper destination, at the summit of the plant : the 

 root was no longer wanted, hut to yield that trifling degree of 

 sap required to support the stem; all its other juices and nourish- 

 ment proceeding irom the cuticle of the leaf. 



The leaves of sand plants have three cuticles above and two 

 below; two of each being impervious to water or any liquid. 

 The pabulum, scarcely thicker than the bark juices, is filled with 

 a glutinous matter, which however hardens as the age of the 

 leaves increases. But of all the vegetable tribe no plants possess 

 so many hairs as the sand plants : sometime they are laid hori- 

 zontally in layers both above and below the leaves, as at Plate 1, 

 fig. 1. the chenopodium olidvrn ; sometimes standing perpen- 

 dicularly as in the turnip leaf, fig. 2, but in that case it has al- 

 ways 



