THE OLIVE TRIBE. 1^7 



the Olive tribe, the organization of whose flowers is 

 remarkably uniform. 



For example, the Olive has a shorter corolla and a 

 hard bony nut in its fruit ; the Phlllyrea, with its 

 beautiful deep-green leaves, is exactly like the Olive 

 in the structure of its fructification, but its nut is 

 brittle instead of bony ; and the fragrant Lilac 

 (Syringa) differs from all these in its longer corollas, 

 and in its fruit being dry, and splitting into two 

 valves. 



Simple as is the character of the Olive tribe, and 

 uniform as the genera usually are in their structure, 

 there is one most remarkable exception, which I should 

 not omit to notice. The Ash (Fraxinus), which you 

 know by its smooth and graceful trunk, and by the 

 airy appearance of its light and elegant foliage, is a 

 plant without any corolla, and yet it belongs to the 

 Olive tribe. It may seem exceedingly strange that a 

 plant which has no corolla should be classed with 

 those w^hich have a perfect monopetalous one, and if 

 such a thing were to happen in an artificial system it 

 would be extremely improper, but in a natural ar- 

 rangement all single characters are subordinate to the 

 mass of characters, and, when they do not accord with 

 the usual structure, form exceptions to general rules. 

 Thus, as the Ash agrees with the Olive tribe in every 

 character except the absence of the corolla ; that 

 absence is only reckoned an exception to the general 

 fact that the Olive tribe has a monopetalous corolla. 

 It happens that we possess a striking proof, beyond 

 what the fructification affords, that the Ash and Olive 



