ARRANGEMENT OF ORGANS. 5 



and the same holds good very generally, when the 

 parts of the flower are uneven in number, as in 

 the very common quincuncial arrangement of the 

 sepals, &c. 



To these general remarks, intended to show the 

 agreement between the disposition of the leaves of the 

 stem and those of the flower, it is merely necessary to 

 add that the arrangement of the placentas, as well as 

 that of the ovules borne on them, is also definite, and 

 takes place according to methods explained in all the 

 text-books, and on which, therefore, it is not necessary 

 to dilate in this place. 



The branches of the stem or axis correspond for the 

 most part in disposition with that of the leaves from 

 the axils of which they originate, subject, however, to 

 numerous disturbing causes, and to alterations from 

 the usual or typical order brought about by the 

 development of buds. These latter organs, as it seems, 

 may be found in almost any situation, though their 

 ordinary position is in the axil of a leaf or at the end 

 of a stem or branch. 



The points just mentioned are of primary import- 

 ance in structural botany, and as such are seized on 

 not only by the morphologist, but by the systematic 

 botanist, who finds in them the characters by which 

 he may separate one group from another. Thanks to 

 the labours of those observers who have devoted their 

 attention to that difficult but most important branch of 

 study, organogeny, or the investigation of the develop- 

 ment of the various organs, and to the researches of the 

 students of comparative anatomy or morphology, the 

 main principles regulating the arrangement and form 

 of the organs of flowering plants seem to be fairly well 



