PREFACE. 



The first idea of the present system suggested itself to the Author from a conviction that we have no great difficulty to overcome to arrive at the natural system of the 

 monopetalous families taken separately from the polypetalous, the only defect likely to prove unaccountable being the comparative isolation of certain families, such as 

 Ericaceae, Ebenaceae and their allies, which are not nearly related to any part of the monopetalous series. This being effected, could we then determine in each instance of the 

 polypetalous families, of what monopetalous family it was the polypetalous representative, a natural arrangement of the polypetalous families would then as it were form 

 itself ; the natural system of the monopetalous families being thus made use of to explain to us what has hitherto been the greatest desideratum in systematic botany, viz., the 

 natural system of the polypetalous. This result being obtained, the apetalous families could then without difficulty be arranged according to their nearest affinities, the 

 polypetalous being in their turn taken as a guide to the true station of each of the apetalous. In attempting however to accomplish a task including so many inquiries he has 

 employed also, and quite as frequently, the reverse mode of comparison, commencing with the apetalous; and as far as it has appeared to him that either of these modes of 

 comparison has proved successful, it has been rigidly adhered to in the formation of the present system. 



It will be found that the present arrangement is very different from that in the Ann. Nat. Hist. 2nd Ser. vol. XI. In attempting to complete and fill up the outlines of 

 that arrangement by the addition of the results of new observations, it was soon found to be in its primary divisions impracticable, just as the discovery of new genera proved 

 that the artificial system of Linnasus was impracticable. But of the present arrangement he is able to say, that for the last four or five years it has undergone no material 

 alteration, all the new facts and observations which have since been made or become known, proving to be, as he views them, in harmony with the present arrangement, and in 

 not a few instances materially improving and confirming it ; and to be able to add this, after having applied to it so severe a test as the discoveries made known to us in 

 Bentham and Hookers ' Genera Plantarum] will, he trusts, remove the objection to which he has referred as applying to the arrangement in the Ann. Nat. Hist. 



The main feature of the present arrangement, after having placed the apetalous, polypetalous, and monopetalous families in their mutual relations to each other, is the 

 complete detachment of the Epigynous families as a distinct Division of the Class Exogens, the unisexual and many other families really belonging to that Division having 

 hitherto been kept separate, or placed in other Divisions. His conviction is, that the Epigynous Division will prove to be as really distinct from the great mass of Exogens as 

 the Endogens are from Exogens, and he has therefore given unremitting attention to form a correct line of division between the Epigynous and the great mass of Exogens, 

 because it is obvious that if the existence of such a division could be demonstrated, the study of systematic botany, especially to students, would be much facilitated. 



Since the appearance of the Tables, in 1853, (Ann. Nat. Hist. 2nd Ser. vol. XI.,) he has verified where there was any remaining doubt, and in many instances repeatedly, 

 the observations as regards the position of the carpel when single, and of the raphe, and has had to correct only Brunoniacese among the former, (the alteration not being the 

 consequence of error in observation, but of a different conclusion with respect to relative position,) and Nolanaceae, Ehretiacese, Globulariaeeas, and Crassulaceae and 



