l68 LETTER XI 11. 



are both very nearly related to each other. It is well 

 known that no tree can be either budded or grafted 

 upon another, unless they are extremely nearly related 

 by natural ties ; the Olive may be grafted upon the 

 Ash, and consequently the inference that is drawn 

 from the construction of the flowers is confirmed by 

 the physical properties of the two plants. 



I told you but a short time since that there were 

 two monopetalous natural orders with regular flowers, 

 in which there are only two stamens. The one 

 to which as yet no allusion has been made, is the 

 Jasmine tribe, to which belong the many fragrant 

 plants which bear that name. These are known by 

 a most simple character from the Olive tribe ; the 

 edges of the divisions of their corolla, instead of being 

 exactly fitted to each other before the flowers ex- 

 pand, overlie each other in the bud, and slide off 

 each other when they unfold. These differences 

 give rise to two technical expressions which I cannot 

 do better than explain to you on the present occa- 

 sion. 



We call the manner in which the parts of the 

 flower are folded up in the bud the (Estivation ; and 

 we apply the term either to the calyx or corolla, or 

 stamens, or pistils, with some qualifying adjective. 

 When two parts are placed together, edge to edge, so 

 that one does not lie at all upon the other, those parts 

 are said to be valvate, and when they do lie upon each 

 other, they are said to be imbricated, or tiled, in al- 

 lusion to the manner in which tiles (called in Latin 

 imbrices) are placed upon the roof of a house. These 



