154 APPENDAGES OF THE STEM. 



the bottom or broken part of the midrib ; this in- 

 creases to a kind of tuber which, after a time, ejects 

 both radicles and stems, a clear proof that detach- 

 ments of the vital membrane are projected into the 

 leaves. 



Leaves are, except in some of the Coniferce, 

 always closely connected with the buds : indeed, it- 

 seems the former are only detachments of the bark 

 to permit the escape of the latter. They generally 

 accompany each other ; and in some kinds of trees 

 the buds are formed within the base of the petiole. 



Amplitude and deep colour of the foliage are sure 

 signs of high health and vigour, as a pale colour 

 and diminutive size of leaves are indications of 

 weakness or disease. So the rugose texture of their 

 surface is a mark of barren luxuriance, whilst com- 

 pactness and polished appearance of the disc, indi- 

 cate not only perfect health, but fruitfulness also. 

 This is strikingly visible on the grape-vine, melon, 

 and strawberry : the reason is, perhaps, that the 

 swelling fruit requiring a large share of the rising 

 sap, checks the expansion of the leaves, and ren- 

 ders them firmer in texture and less in size. 



From the state or changes of the leaves it is quite 

 evident, that though the root be the chief organ for 

 supplying the nutriment of the plant, the leaves are 

 certainly the exciters of what may be called the 

 appetite. They are constantly, especially under the 

 action of a cloudless sun, craving supplies. Their 

 surfaces all turned sunward, receive both light and 



