220 ' OF TIIi: FL'LCKA, 



. just above their insertion. The Enropeean 

 • Ritbiacece have whorled leaves, as Aspc- 

 villa, Galium^ Rubia, Sec; but Asperula 

 CT/itanchica, Engl. Bot, f . 33, has some- 

 times two of its four leaves so small as to 

 look like stipulas, seeming to form an inter- 

 mediate link between such as have whorled 

 leaves and such as have opposite ones with 

 stipulas. The next step from Asperula is 

 jyiodia, and then Spermacoce. In the two 

 last the bases of the stipulas and footstalks 

 are united into a common tube. 



Some stipulas fall off almost as soon as 

 the leaves are expanded, which is the case 

 with the Tulip-tree, Liriodendron tuUpi- 

 fera ; in general they last as long as the 

 leaves. 



The absence or presence of these organs, 

 though generally an indication that plants 

 beiono' to the same natural order and even 

 genus, is not invariably so. Some species 

 ot Cist us have stipulas, others none, which 

 is nearly the case with grasses. The 

 stipula in this, one of the most distinct 

 of all natural orders, is peculiar, consisting 

 of an internal white membrane crowning; 



