CHAP. II. 
LEAVES. 
Ill 
radiating leaf that the curve-veined bears to the straight- 
veined ; it is the folium penninervium of De Candolle. 
10. Hidden-veined (introvenium) , To this I refer all leaves 
the veins of which are hidden from view by the parenchyma 
being in excess, as in Hoya, and many other plants. Such a 
leaf is often inaccurately called veinless. De Candolle calls 
a leaf of this nature, in which the veins are dispersed through 
a large mass of parenchyma, as in Mesembryanthemum, 
vaginervium. 
It may be necessary to explain the direction that the 
primary veins take when they diverge from the midrib : this 
can be denoted by measuring the angle which is formed by the 
midrib and the diverging vein, and can either be stated in 
distinct words, or by applying the following terms thus : — if 
the angle formed by the divergence is between 10° and 20 , 
the vein may be said to be nearly parallel [subparallela) ; if 
between 20° and 40°, diverging ; between 40° and 60°, spread- 
ing ; between 60° and 80°, divaricating; between 80° and 90°, 
right-angled; between 90° and 120°, oblique; beyond 120°, 
refiexed {retroflexa) , 
With regard to the forms of leaves^ this subject properly 
enters into Glossology ; because the terms applied by Botanists 
to differences in the outline of those organs are, in fact, ap- 
plicable to any varieties in the figure of any other flat body. 
Nevertheless, as it may be a matter of convenience to the 
student to l^now upon what principles the most remarkable 
forms of leaves, or of other divided parts, are thought to be 
connected with each other, I here translate the observations 
upon the subject made by Alphonse de Candolle, whose recent 
Introduction to Botany may be supposed to embody the latest 
opinions of his father. 
" Leaves put on a multitude of forms, depending upon the 
manner in which they are severally organized, especially with 
regard to their division and the direction of their veins. 
These veins being in general symmetrical on the two sides of 
the midrib, leaves themselves are almost always of some 
regular figure, as, for instance, oval, rounded, elliptical, &c. 
Their regularity, however, is never mathematical ; and there 
