THE BUCK-THORN TRIBE. 119 



placed on slender stalks, and in room of the stipules, 

 which are characteristic of the greater part of the 

 Tribe, they have a pair of sharp slender spines, which, 

 upon the old branches, are curved outwards, and 

 become so strong as to render hedges, made from the 

 plant, perfectly impenetrable. 



The flowers are pale greenish yellow, small, and 

 grow in little stalked clusters, which are much shorter 

 than the leaves themselves. They have a flat spread- 

 ing calyx, divided into five sharp lobes {fig. 2. b. &.), 

 each of which is a little raised in the middle, and ac- 

 curately fitted to the edge of its neighbour before the 

 flowers expand; so that, although the edges do not 

 overlap each other at all, they nevertheless form a com- 

 plete closed cavity, in which the stamens and petals are 

 enclosed. This is one of the marks of the Buck-thorn 

 Tribe, and is called a valvate cestivation (See Vol. I. 

 p. 168.). 



Alternately wath the divisions of the calyx are placed 

 five little yellow hoods (fig. 2. a. «.), which completely 

 cover over the stamens ; they are the petals. Oppo- 

 site the petals are the five stamens ; this is the next 

 circumstance that you are particularly to attend to ; 

 there are very few instances where the stamens are 

 opposite the petals, and also of the same number, and 

 when it occurs it is always esteemed a structure of 

 importance. After the stamens comes a broad, orange- 

 coloured, lobed, flat disk (fig. 5. a. Si fig. 2.), which 

 does not touch the ovary, but simply lies upon the 

 spreading sides of the calyx. The ovary is a little 

 buried in the calyx at the bottom (fig. 5. />.), but 



