CHAP. II. 
STIPULES. 
121 
term. When they are membranous, and surround the stem 
like a sheath, cohering by their anterior margins, as in Poly- 
gonum {Jig. 61.), they have been termed oc/irea by Willdenow. 
Of this the fibrous sheath at the base of the leaves of Palms, 
called reticulum by some, may possibly be a modification. In 
pinnated leaves there are often two stipules at the base of each 
leaflet as well as at the base of the common petiole : stipules, 
under such circumstances, are called stipels. 
The exact analogy of stipules is not well made out. De 
Candolle seems, from some expressions in his Organographies 
to suspect their analogy with leaves ; while, in other places 
in the same work, it may be collected that he rather con- 
siders them special organs. I am clearly of opinion that, 
notwithstanding the difference in their appearance, they are 
really accessory leaves : first, because occasionally they are 
transformed into leaves, as in Rosa bracteata, in which I have 
seen them converted into pinnated leaves ; secondly, because 
they are often iindistinguishable from leaves, of which they 
obviously perform all the functions, as in Lathyrus, Lotus, 
and many other Legumhiosae: and, finally, because there are 
cases in which buds develope in their axils, as in Salix, a 
property peculiar to leaves and their modifications. De 
Candolle, in suggesting, after Seringe, that the tendrils of 
Ciicurbitaceae are modified stipules, assigns the latter a ten- 
dency to a transformation exclusively confined either to the 
midrib of a leaf, or to a branch ; and they cannot be the 
latter. 
It is sometimes difficult to distinguish from true stipules 
certain membranous expansions, or ciliae, or glandular append- 
ages of the margin of the base of the petiole, such as are 
found in Ranunculacese, Apocyneae, Umbelliferas, and many 
other plants. In these cases the re^l nature of the parts is 
only to be collected from analogy, and a comparison of 
them with the same part differently modified in neighbouring 
species. 
De Candolle remarks, that no Monocotyledonous plants 
have stipules; but they certainly exist, at least in Fluviales 
and Aroideae. It is also said that they do not occur in the 
embryo ; but then there are some exceptions to this opinion, 
