518 MR. J. PARKIN ON THE 
Müller * of fairly recent date may be mentioned, as in it full reference is 
given to the former work on this branch of the subject. As this paper does 
not profess to extend to a detailed consideration of these peculiar inflores- 
cences, farther reference to this part of the literature becomes unnecessary. 
III. Tae GENERAL CHARACTER AND BIOLOGICAL SIGNIFICANCE 
OF THE INFLORESCENCE. 
The main feature which distinguishes an inflorescence from a solitarily 
placed flower is that in the former there are several (two or more to be 
accurate) flowers clustered together without foliage leaves intervening, while 
in the latter there is only one. That is to say, inflorescences come to be 
formed by the production or segregation of flowers apart from the foliage. 
The lateral axes terminated by flowers—the usual components of an 
inflorescence—like ordinary vegetative shoots, are each borne in the axil of a 
leaf-structure, but this is no longer foliar in character; it is a much reduced 
organ with little or no assimilating tissue, termed the bract. The lateral 
(secondary) axis may also bear, besides its terminally placed flower, similar 
reduced leaf-structures 
usually a pair in Dicotyledons—known as bracteoles. 
These may bear in their axils tertiary flower-shoots of a like nature, and in 
some inflorescences higher series still may be produced : thus the bracteole of 
one axis becomes the bract of the next and so on. 
In many inflorescences, usually ones few flowered and lax in habit, there is 
no sharp line between where the foliage leaves end and the bracts begin. 
There is a gradual diminution in the laminze of the leaves bearing flowers 
from below upwards, unti! in the last produced flowers the lamine have 
disappeared totally and the bract becomes a truly non-assimilating organ. 
Such inflorescences the author regards as having remained in a primitive 
stage. The degree of sharpness with which the inflorescence is marked. off 
from the foliage, shows in a general way the amount of progress in its 
evolution. The capitulum of the Composite, the catkin of the Amentacer, to 
take two examples, represent advanced tvpes of inflorescence, as the flower- 
cluster in each case is sharply marked off from the foliage. 
Three other prominent features showing advancement in the inflorescence 
may be mentioned here, viz.:—the suppression of internodes resulting in 
compact clusters, the abortion of bracts or bracteoles or both as in the 
Cruciferæ, and the differentiation of the individual flowers into two or some- 
times three quite dissimilar kinds with definite arrangement of these, e Jey 
many Composite, Muphorbia, Ficus, Arum, ete. Inflorescences of the last 
type may be looked upon as the highest phylogenetically. 
In the first paragraph of this section of the paper the words “ production ” 
* Muller, W., * Beitrage zur Entwicklungsgeschichte der Inflorescenzen der Boragineen 
und Solaneen,” Flora, xciv, p. 385, 1905. 
