THEIR FORMS AND FUNCTIONS. 48] 
Zizyphus rugosa, Lam., has larger, roundly oval leaves. One 
stipule stands straight out at right angles to the axis, while 
the other remains nearly erect, but incurved towards the axis. 
The terminal bud in the growing state is protected to a slight 
extent by their stipules, but more effectively by the tomentum 
on the underside of the leaves, and by the large size the latter 
attain before expansion. 
In Paliurus australis, Gertn., the stipules serve two pur- 
poses. They are spiny and dimorphic. On the strong upright 
young stems they are largest and longest, subulate, slightly 
decurved, and equal or nearly so. On the more slender lateral 
shoots with distichous leaves they are very unequal in size and 
dissimilar. Those on the upper side of the branches are the 
longer, subulate, long-pointed, straight, ascending in two ranks, 
one to the right and the other to the left, according to the side 
of the shoot on which it is developed. On the lower face of the 
shoots they are short, subulate, and decurved or hooked, and 
arranged in two ranks, as are those on the upper face of the 
shoots. 
In the bud state they are erect, greatly elongated, in fact often 
longer than the leaves to which they belong, acutely pointed, but 
as yet quite soft. Their numbers would afford some protection 
to the leaves in the bud state, as the latter are crowded; but the 
chief object would seem to be that the straight ones protect the 
plants from browsing animals, while the hooked ones would not 
only answer the same purpose, but assist the plant to climb or 
scramble up amongst other bushes or shrubs. 
In Ceanothus rigidus, Nutt., the stipules in the full-grown state 
are triangular, obtuse, short, stout, or thick at the base, rigid, 
pale reddish brown, persistent. 
They attain their full size while still in bud, and while the latter 
is compact they equal the leaves in length. At this stage they 
are ovate and pointed; but as they get older the thinner and 
more membranous part becomes brown and falls away. They 
therefore serve to protect the young leaves in the bud state ; and 
as the internodes become elongated a little behind the growing 
apex, they{constitute a good protection to the axillary,buds, which 
begin to develop at a very early stage of the growing shoot ; in 
fact, they are almost coeval with the terminal bud, developing 
one or two pairs of leaves on very short shoots in the axils of the 
leaves of the primary axis, and then in the majority of cases become 
