8 On the Nourishment produced to the Plant ly its Leaves. > 



first consider^ but which, from tlie extraordinary diiference of the 

 formation of their leaves, well deserves a place here, I have 

 long before shown, that plants flowering in the leaf teach more 

 than any other vegetable I am acquainted with, as drawing an 

 exact division between those ingredients wanted to Jorm the 

 flower, and those merely required Jbr the leaf only. It was 

 thethorough study of these plants that first taught me the com- 

 plete distinction between thcni, which has been of more use to 

 me than almost any dissection I could name, as drawing a very 

 exact and precise line never infringed by nature, and enabling 

 me to avoid that confusion perpeiualli/ to be observed in many 

 authors in describing the flower and the leaf. The leaf alone, 

 as I have shown before, is formed of much bark ; a very trifling 

 degree of wood ; a pabulum composed of the bark juices j quan- 

 tities of spiral Avire; and much of that impervious skin often de- 

 scribed, and which prevents the leafs too great evaporation : 

 but when the flower is to be placed within it, then the line of 

 hfe is added, a great deal more wood, and the pabulum de- 

 creased ; and in its place the flowers and seeds fill ujj the in- 

 terior : see fig. 12. This sort of leaf is always sliffcr and harder, 

 as having such a quantity of wood to convey the sap to the 

 flower; and it proves this to be its purpose, by the manner in 

 which the sap vessels lie. In the xylophylla (which flowers in 

 the contour of the leaf) all the sap vessels run from the midrib 

 to the edge, with an open mouth at the hud. In the ruscus 

 (which flowers in the middle of the leaf) the sap vessels, after 

 running in the shape of a heart, arrange themselves in the centre 

 and stop at the middle point, while in the fern (where the leaf 

 flowers in the direction of the spires) the sap passes on to the 

 line of the flower, and there stops. This description may ap- 

 pear trifling; but a minute knowledge of the formation of every 

 part of tlie vegetable, clear and without confusion, can alone 

 enable us to profit by every accidental fact nature presents us 

 with, and to which perpetual watching makes me a witness. 

 I have seen so much confiision arise from endeavouring to ac- 

 count for facts without this acqtiirement, that I shall never but 

 rejoice that it was the very first object of my search; nor can I 

 ever think it can be too minutely exact, or too perfect, since 

 I am convinced that that knowledge can alone serve as a foun- 

 dation for the more useful studies of gardening and agriculture. 

 It is the first step of the ladder. I cannot leave this species of 

 plant without mentioning how completely they prove that sub- 

 ject I have so much at heart, that " all vegetables form the heart 

 or essence of the seed in the root." In the fern in particular, 

 the seeds arc to be traced not only all up the stem, but through 



the 



