STIPULES. 167 



technical language of the botanist, are termed Stipule*. 

 They are usually found in pairs at the base of the peti- 

 ole, Fig. 20, and this Dr. Smith regards as their most 

 natural position. 



In the Myrtle-leaved Pea-vine they are semi- sagit- 

 tate, resembling a section of the arrow-shaped leaf; in 

 the Willow, they are frequently lunulate, having the 

 appearance of the crescent-shaped leaf ; in the Silver 

 weed they are ovate ; in the common Pea they are 

 round ; and in other plants they assume other figures 

 designated by terms which have been defined in a for- 

 mer chapter. 



In the examples which have been enumerated,- the 

 stipules are in pairs, exterior to the leaf; and in some 

 of them, and also in the Rose, they are laterally united 

 to the. petiole at its base. In other plants, the stipules 

 are internal and simple, as in the Knot-grass, and other 

 species of Polygonum. In these it is frequently tubu- 

 lar, forming a sheath for the stem above the insertion 

 of the petiole ; and to this peculiar variety of the sti- 

 pule, those who are fond of minute distinctions have 

 applied the term Gchrea. 



In the natural order of Grasses it is also solitary, form- 

 ing a membranous scale, which arises from the summit 

 of the sheath, and like it encloses the culm. This 

 form of the stipule is denominated ligula, a term which 

 Dr. Smith regards as superfluous, and of course to be 

 rejected. It is however still retained by several wri- 

 ters, and not unfrequently occurs in the delineations of 

 American grasses. Usually the stipules are persistent, 

 and fall only with the leaves, but in the Tulip-tree they 

 are deciduous and fail as soon as the leaves are fully 

 expanded. The presence and figure of this organ are 



©ften the basis of botanical distinctions and Jussieu 



15 



