246 ON THE FORM OF THE LEAF OF VIBURNUM. 
leaves, more or less oval or ovate. This would appear to be the 
form typical or original to the genus. 
Now let us suppose that, either from having extended north- 
wards (and both Viburnum Lantanaand V. Opulus are among the 
northern representatives of the genus), or from some other cause, 
the young leaves require additional protection. This may be 
effected in several ways. For instance, the young leaf may be 
guarded by a thick coat of felted hairs: this is the case in 
V. Lantana. Another plan would be that the outer leaves 
should become leathery and thus protect the inner ones: this 
is the case with V. Opulus. But that being so, it is an advant- 
age that the inner or true leaves should be folded, because 
they thus occupy less space. This perhaps accounts for the 
folding of the leaves of V. Opulus in the bud, while the lobes 
follow from the mode in which the leaves are folded. Now 
a leaf folded up as are those of V. Opulus requires only two 
or three lateral veins. The remaining veins, then, and the 
membrane connecting them, will gradually be reduced, and 
ultimately disappear. 
In V. Opulus, as is shown in the figure, there is a space left 
Viburnum Opulus. Bud, X 4.—L.L, lateral lobes of leaf ; Z, one of next 
younger pair of leaves; St, stipule. 
between the bases of the leaves. In the Acers, many species 
of which have leaves somewhat resembling those of V. Opulus, 
this space is fully occupied by the following pair of leaves. 
This, however, is not the case in V. Opulus, and the space thus 
left unoccupied is filled up by the stipuliform appendages. I 
