CHAP. II. STIPULES. 121 



term. When tliey are membranous, and surromid the stem 

 like a sheath, cohering by their anterior margins, as in Poly- 

 gonum (^^.61.), tliey have been termed ocArm 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 wth 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 luidistinguishable from leaves, of which they 

 obviously perform all the functions, as in Lathyrus, Lotus, 

 and many other Leguminosae: and, finally, because there are 

 cases in winch 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 

 Cucurbitaceae 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 cilise, or glandular append- 

 ages of the margin of the base of the petiole, such as are 

 found in Ranunculaceae, Apocynea?, Umbelliferae, and many 

 other plants. In these cases the real 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 Aroidea?. It is also said that they do not occur in the 

 embryo ; but tlien there are some exceptions to this opinion, 



