234 Dr Daubcny un the Writhigs and 



them under distinct heads, in a manner which renders their 

 subsequent recollection a matter of comparative facility. 



It is the same with respect to the several varieties of leaves, 

 which are rendered much more easy of recollection, in conse- 

 quence of being first reduced to two great heads, characteris- 

 tic of the two natural divisions of plants into monocotyledo- 

 nous and dicotyledonous ; then subdividing the former into 

 those with convergent and divergent nerves ; and the latter, 

 into the four heads of penninerve, peltinerve, palminerve, and 

 pedalinerve, if simple, and of pinnate, pellate, palmate, and 

 pedalate, if composite, thus limiting the effort of memory 

 chiefly to the task of distinguishing the several terminations, 

 which, from their great variety, do not seem reducible to any 

 such principle of classification. 



But the most successful application of physiological princi- 

 ples to terminology occurs in the chapter in which Mons. 

 Decandolle has availed himself of Roeper's ingenious method 

 of distinguishing the various modes in which flowers are situat- 

 ed upon their stalk, which, under the name of their inflorescence, 

 has given rise to so much confusion, but of which, neverthe- 

 less, our countryman Robert Brown, in his Memoir on the 

 Compositae, published in 1818, shewed that he had entertained 

 a just conception.* 



Instead of contenting himself with merely setting down the 

 names and dispositions of their respective kinds, as of the Ver- 

 ticillum, the Raceme, the Spike, the Corymb, the Fascicle, the 

 Capitulum, the Umbell,the Cyme, the Panicle, &c., Decandolle 

 begins by noticing, in the first place, the two difi^erent plans 

 upon which the evolution of flowers may proceed — the ten- 

 dency in some cases being towards, in others away from, the 

 centre of the tree. The first he denominates centripetal, the 

 latter centrifugal inflorescence. 



He further finds, that some of the kinds observed by bota- 

 nists are modifications of the centripetal, others of the centri- 

 fugal tendency ; and he goes on to point out, how one kind is 

 related to another, how it may graduate into it, and how cer- 

 tain species of inflorescence (such as a capitulum) may arise 

 out of either of these tendencies, and therefore cannot be re- 



* See also a Memoir bv M. Tiirpiu in the 5th volume of the Mcmoircs 

 du Museum, 1819. 



