CHAP. II. THE STIPULE. 73 



species, but one of the most prevalent forms is that 

 of the half arrow-shaped, as in the genus 

 Lathyrus and many species of Willow. In the 

 Grasses they are merely a sort of thin scale (PL III. 

 Fig. Q.) crowning the sheath of the leaf, and with 

 it investing the stem. In the genus Pinus they 

 consist of a dry and scariose membrane (PL III. 

 Fig. 10.) investing the leaves by the base. This is 

 at least the case in such species as produce their 

 leaves in pairs, as in Pinus sylvestris. 



Sometimes the stipulae are solitary, as in the 

 Grasses ; but they are for the most part protruded in 

 pairs, one on each side the base of the expansion or 

 foot-stalk, as in the Vetch and Weeping Willow. In 

 the genus Hdianthemum they are protruded in fours. 

 In their insertion they are generally altogether dis- 

 tinct from the leaf; but in the genus Rosa and 

 some others they are attached to it by the one side. 

 There are also other varieties in the mode of their 

 insertion, from which botanists have divided them 

 into such as are extrafoliaceous and such as are in- 

 trafoliaceous ; the former originating in the stem 

 but rather below the insertion of the leaf, as in the 

 cases already quoted ; the latter originating in the 

 stem also, but situated rather above the insertion, or 

 in the axil of the leaf, as in Primus Padus or Bird 

 Cherry. In many plants, particularly of the natural 

 order of RubiacecE, the stipulae which are intrafolia- 



ceous form a sort of tube or sheath investing the 



o 



stem immediately above the insertion of the foot- 



