STIPULES. 



171 



plants ; but their presence or absence is usually uniform throughout 

 a natural order. Stipules assume a great variety of forms analogous 

 to those of the blade. Like it they are sometimes membranaceous 

 or scale-like, and sometimes transformed into spines, as in the Locust- 

 tree, &c. They are sometimes present on developing shoots 

 only; as in the Beech, the Fig, and the Magnolia (Fig. 155, 15G), 

 where they form the covering of the buds, but fall away as the 

 leaves expand. They have a strong 

 tendency to cohere with each other, or 

 with the base of the petiole. Thus, in 

 the Clover (Fig. 304), the Strawberry, 

 and the Rose (Fig. 281), a stipule ad- 

 heres to each side of the base of the 

 petiole ; in the Plane-tree, the two are 

 free from the petiole, but cohere by 

 their outer margins, so as to form an 

 apparently single stipule opposite the 

 leaf. In other cases, both margins ; re 

 united, forming a sheath around the 

 stem, just above the leaf: these are 

 called intrafoliaceous stipules ; and 

 when membranaceous, as in Polygo- 

 num (Fig. 305), they have been termed 

 ochrece. When opposite leaves have 

 stipules, they usually occupy the space 

 between the petioles on each side, and 

 are termed interpetiolar. The stipules 

 of each leaf (one on each side), being 

 thus placed in contact, frequently unite 304 303 



so as to form apparently but a single pair of stipules for each pair 

 of leaves ; instances of which are very common in the order 

 Pvubiaceas. 



306. Leaves furnished with stipules are said to be stipulate : when 

 destitute of them, exstipulate. The leaflets of compound leaves are 

 sometimes provided with small stipules (termed stipelles) of their 

 own, as in the Bean (Fig. 286) ; when they are said to be stipellate. 



FIG 304. A leaf of Red Clover, with its three leaflets at the summit of the leafstalk, to 

 which at the base the stipules (st) are adherent, one on each side. 



FIG. 305. Part of a lenf of Polygonum orientale, with iU stipules united into a Bueath 

 (ochrea) and surrounding the stem. 



