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, &e. 
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 
