ANONACEJE. 249 



even with their edges not at all in contact. In the corolla the 

 aestivation has served to distinguish considerable groups, such, for 

 example, as the U/ionc/s and Uvariea. But on this point we must 

 insist less than most authors ; for in the genus Ucaria some species 

 have both corollas imbricated, others the one imbricated the other 

 valvate ; Anona, whose petals are usually valvate, may have them 

 most markedly imbricated,' as is the case too in certain Unonas of 

 the group PoI^aHhia.- 



2. The conformation of the pieces of the perianth, their form and 

 relative size. — This character is another which has been placed in 

 the first rank, having been used by Bentham & Hooker to estab- 

 lish all their tribes except one ; and these botanists have, as we have 

 seen, distinguished the three corollas which they term of the Unonece, 

 Xi/lopiecB, and Mitrophorece. That these forms are well marked 

 towards the culminating points of these groups is incontestible, 

 and hence we have avoided neglecting such a character in the sub- 

 division of the great group Anoncm into minor sections. But we 

 have not founded true series on it, because there is one common type 

 of structure towards which all these forms gradually converge, so 

 that we get stages in which we cannot surely distinguish the Uno- 

 nean type of corolla from the Mitrophorean or Xylopiean. Of 

 this we have cited numberless proofs ; here it will be sufiicient to 

 recall the fact that in the Melodoram group alone (including Pyra- 

 midanthe) there are at the same time corollas of JJiiona and Xylopia, 

 and that we find the same thing in Jnona, Boccif/ea, &c. ; while 

 the conformation of the perianth of Pojjowia has caused it to 

 be classed by some among the Unonece,^ by others among Mitre- 

 phorece.* Thus, again, it is because structural characters derived 

 from the relations of form and size stated to occur in the different 

 pieces of the perianth are by no means absolute, that we have 

 proposed as of practical utility and convenience, though in no 



^ See especially what we have said relative to genera, and will no doubt lead to a fresh reduc- 



the corolla of A. muricata (p. 222). tion in their total number. 



3 B. H., Gen., 25, n. 19. It is true that the 



2 We know, and shall at some future time de- authors add to their description : " Genus vixrile 



scribe several Old World plants that can hardly limifa/i/m." 



be referred elsewhere than to Poh/allhia, though ■* Hook. F. & Thoms., Fl. Ind., i. 105. Cer- 



their petals are distinctly imbricated. It may tainly tho corolla of the Asiatic species is in most 



be easily divined how they are also closely allied cases rather that of the Fhaantheiv than that 



to the genus Cananfja (Guatferia). Perhaps, of the J/<7rf/>//ore<E proper or the I'lioneiv; but 



then, the future will compel us to recast certain they cainiot be separated from the African species. 



