PEEFACE. IX. 



and genera. There must, indeed, necessarily be mucli that is 

 purely arbitrary in the linear series, which is not natural, but which 

 we cannot avoid, and much that is arbitrary also in the rank 

 assigned to subdivisions. It is more practical convenience than the 

 observation of fact that must decide whether a family be divided 

 into a certain number of suborders or tribes, each containing so 

 many genera divided again into subgenera or sections, or whether 

 the suborders should rank as famibes, the genera as suborders or 

 tribes, the subgenera or sections as independent genera. But this 

 very motive of practical convenience, should induce writers of local 

 Floras and partial Enumerations to take as their general guide 

 some one standard work (say the ' Prodromus ' of De Candolle, as 

 that whose merit is the most generally recognized), only inti'oducing 

 such partial innovations and improvements as may meet with uni- 

 versal approbation. Our ovra most recent standard Floras have 

 fortunately taken that course, and the Author of the present Work 

 has only had to follow their example. The few deviations he has 

 made in this respect from the ' British Flora ' of Hooker and Arnott 

 have been chiefly the retaining as subdivisions some of the groups 

 recently raised to independent families or genera, or the trans- 

 position of small families or isolated genera whose af&nities have 

 become better understood. 



The special purpose of the present Flora has induced the omission, 

 in numerous instances, of microscopical, anatomical, or theoretical 

 characters, often of the greatest importance in scientific botany, 

 but useless to the mere amateur. His object is either to identify 

 the plants he gathers in his walks with those he hears or reads of, 

 or to collect and classify the vegetable productions of his neighbour- 

 hood, so as to comprehend, in some measure, the wonderful variety 

 in the mechanism they display for the development of one general 

 plan, or to illustrate in one small item the inexhaustible vastness of 

 Creation. Should he wish to plunge deeper into the science, and 

 become a professed botanist, he must enter upon the study of 

 exotic plants, and avail himself of the excellent elementary treatises 

 and other works supplied by the scientific botanists of this and 

 other countries. 



Similar considerations have induced the omission of detailed 

 characters of such large exotic Orders as are represented in Britain 

 only by single, often anomalous, genera or species. The Violet, 

 the Maple, the Lime, the Milkwort, etc., can, in a British Flora, 



