EVOLUTION OF THE INFLORESCENCE. 525 
After this digression, let us now turn to the consideration of the solitary 
terminal flower in the Dieotyledons. Before doing so, it may be well to 
be clear as to the meaning here attached to the conception of a terminal 
flower. 
Tt has been stated that such flowers are extremely rare ; but the writer in 
question limits the definition to plants in which the plumular (seedling) axis 
ends in a flower. Kerner *, for example, so defines the terminal flower, 
declaring it to Le a rare occurrence found in a few annuals, e. g. Papaver. 
In this paper the word * terminal” is applied to a flower which is produced 
at the end of a leafy shoot, no matter whether such a foliar shoot be the 
primary (plumular) axis or one formed later by branching. Both Van 
Tieghem f and Bentham f allow this wider definition. 
When flowers are borne terminally and singly, then theoreticaily the 
plumular axis should eventually end in a flower. It may be prevented from 
doing so through the apex of the shoot becoming arrested in its growth 
before the plant is in a condition to flower. In this case the first bloom will 
appear, not on the main axis, but on the top of a subordinate leafy shoot. 
Annuals may generally be considered to have sprung from perennials. 
The vegetative period becomes shortened, and the flowering thereby hastened. 
Hence, in such annuals which may be regarded as having sprung from 
perennials with solitary terminal flowers, it is not surprising to find the 
plumular axis ending in a flower. This may have occurred in the perennial 
ancestor, but would not be so obvious, as the first flower would be longer in 
appearing. 
In shrubs and trees of temperate regions, in which the production of 
flowers does not occur at least during the first summer of the plant’s life, the 
upper immature part of the plumular axis will be killed by frost in the winter 
in those forms in which the shoots continue growing all the season ; the main 
stem the next season will then be continued by an axillary bud. An advance- 
ment on the above is shown in many temperate trees and shrubs by the 
plant itself arresting the shoot’s growth in the early summer and forming a 
bud in an apical position, which is destined to continue the main axis the 
following season, This bud may be a truly terminal, or a lateral one 
produced in the axil of the uppermost foliage-leaf—a common occurrence. 
1f the former condition prevails till the flowering stage is reached, then in 
those trees and shrubs with solitary terminal flowers, the first flower will end 
the plumular axis. In the latter condition this can never occur, for the 
* Kerner, A.,‘The Natural History of Plants, London, ed. F. W. Oliver, vol. i, (1894) 
pp. 640-641, 
t Tieghem, P. E. L. van, ‘ Traité de Botanique, 2nd edit. 1891, p. 341. 
t Bentham, ‘ Handbook of the British Flora, 6th edit., by J. D. Hooker, 1892, pp. xxii 
& xxiv. 
