ON LEAVES. 67 



cult to refer the formation of down 01 varnish to the same 

 origin. The scales of buds probably absorb from the sap 

 only a portion of what was destined to nourish them had 

 they been developed into leaves, and the remainder may 

 be converted into a species of glutinous resin or varnish. 

 The rudiments of leaves, when examined in the bud be- 

 fore it is developed, wear the appearance of small fila- 

 ments of cotton, which, when spread out, exhibit the mi- 

 nute skeleton of a leaf. 



It would be difficult to suggest a mode of folding or 

 rolling which Nature has not adopted in enclosing these 

 embryo leaves in the bud. They are sometimes, as those 

 of the vine, folded like a fan ; others are double from the 

 top to the bottom ; others folded down the middle ; some 

 are laid one within another ; others closely packed side 

 by side ; and there are an equal number of modes of roll- 

 ing them up in the buds. 



In some plants the petioles or foot-stalks retain the 

 nourishment they should transmit to the leaves, so as to 

 prevent the latter from being fully developed ; they re- 

 main therefore in an embryo state ; the petiole, in the 

 mean time, gorged with nutriment, becomes thick, cor- 

 pulent, and clumsy, flattening as it expands, and wears 

 rather the appearance of a leaf than of a stalk. The aca- 

 cia of New Holland has this singular conformation. 



Caroline. I have seen tropical plants in hothouses of 

 this description : the prickly fig is, I believe, one of them. 

 But how do these leafless plants disburden themselves of 

 the superfluous moisture which leaves exhale ? 



Mrs. B. The dilated petioles, which usurp the place 

 of. leaves, perform also, though but imperfectly, their 

 functions, and have pores adapted for that purpose : they 

 are not, however, leaves, any more than the tail of a kan- 

 garoo is a leg, or the trunk of the elephant an arm, though 

 they respectively perform the office of these members. 

 When common organs assume in certain species an un- 



357. What becomes of the sap in the branches not needed for the nour- 

 ishment of the scales of the bud! 358. What is said of the rudiments 

 of the leaves when examined in the bud before it is developed'? 359. 

 What are the different ways in which embryo leaves are folded! 360. 

 What is said of the petioles which retain the sap, which they should 

 transmit to the leaves'? 361. What is an instance of this! 362. 

 What is said of dilated petioles which usurp the place of leaves'? 



