64 LEAVES. 
alike in appearance, the absorption of nutritive matter from 
water, or from the vapour diffused through the atmosphere, 
is carried on indifferently by either surface. In trees, th 
— leaves of which have distinct upper and under surfaces, dif- 
fering from each other also in appearance, this absorption 
is carried on only by the under surface. 
_. 222. This was ascertained by Bonnet, who laid on water 
alternately both surfaces of the leaves of many trees and 
herbs, and found that those of the trees lived longest when 
their inferior surfaces were laid on the water; while those 0 
some of the herbs lived equally well with either surface ap- 
plied to the water, and of other herbs, the leaves throve best 
with their upper surfaces next the water. 
223. Some leaves have the power of producing from their 
margins buds capable of becoming new plants. The seeds 
or buds of the Ferns (Filices) are produced in this situation. 
The Bryophyllum and the Marsh Bog-orchis (Malazis palu- 
dosa, Ophrys p. Linn.) also produce buds from the marg 
of their leaves. The buds on the Malaxis are in the form 
papilla, at the extremity of the leaf. 
224. Thus, it will be seen that leaves are organs of 
importance in the vegetable economy : they absorb nutritious 
_ matter from the vapour and other gases diffused through 
the atmosphere; discharge the watery part of the sap by 
evaporation ; expose it to the action of air and light, and 
render it fit for the nutrition of the vegetable. Hence the 
virtues of plants frequently reside in their leaves. 
CHAP. -V.—APPENDAGES,: 
= 225. Streuxes. The stipules are small leafy 
__ at the base of a petiole or sessile leaf, of the same tructt 
___as the leaf to which they are appended, but frequently 
_ different figure. (See Fig. 10, the leaf of White g-Ro 
