218 SIR JOHN LUBBOCK ON STIPULES, 
In attempting to answer this question we may begin by con- 
sidering the function or functions which stipules perform. Of 
these the primary purpose seems to be to protect the bud. In 
other species, however, they serve as accessory or deputy leaves. 
As an illustration of the latter may be mentioned some species of 
Lathyrus, for instance L. Aphaca. 
Passing on now to the cases in which the stipules serve to 
protect the young leaves, I may first mention, in passing, those 
instances in which the stipules with this object have become 
stiff, pointed, and thorn-like, as in Robinia. They are especially 
developed on the lower shoots and branches, which most need 
protection. 
In far more numerous species, however, the stipules protect, 
by enveloping, the young bud and leaves. In such groups the 
view that the function of the stipules is mainly to protect the 
young leaf is confirmed, not to say proved, by the fact that they 
are very short-lived and drop off as soon as the young leaves 
have expanded. Such cases are so numerous that it is hardly 
necessary to quote any illustrations. Indeed, in many of the 
lesser known genera this early fall of the stipules leaves it 
doubtful whether they occur or not. 
On the other hand, there are cases in which protective stipules 
are even more persistent than the leaves to which they belong; 
in such cases, however, they protect, not their own leaf, but that 
of the following year. 
Passing now to the case of Helianthemum, let us compare the 
species which have, with those which have not, stipules. Our 
common H. vulgare (fig. 1) is one of the species with stipules. 
The leaves are oblong-lanceolate, subacute, opposite, petiolate, 
stipulate, channelled above, and thinly covered with stellate 
tufts of hairs, and finely tomentose with similar tufts beneath. 
Some varieties are even more nearly glabrous, others more 
decidedly tomentose. Petiole narrowed to the base, semiterete 
and flattened above, glabrous or nearly so. Stipules subulate, 
acute, one-nerved, ciliate, inserted on the very base of the 
petiole. 
Another species with stipules is H. polifolium. Here the 
leaves are opposite, petiolate, stipulate, lanceolate, obtuse, ter- 
minated by a bristle, channelled above and finely pubescent, 
cariuate beneath, with midrib densely tomentose and hoary. 
The petiole is slightly tapered to the base, narrow, semiterete, 
