Floral Evolution. 
77 
against the suggested primitiveness of those groups which Engler 
has placed at the base of the Archichlamydese, and which are 
represented chiefly by the so-called Amentiferas, and the Urticales. 
In these groups, the female organ consists typically of a single ovule 
associated with two syncarpous carpels. 
These considerations seem to afford no little justification for 
regarding the solitary state of the sporangium as a character not 
primitive, but the result of reduction. This reduction is intelligible 
enough, biologically, for it reflects one of the chief guiding 
principles of vegetable evolution, which we will now proceed to 
discuss in turn. This principle we may name 
1. The Tendency to Economy in Production of 
Reproductive Parts. 
This principle is strikingly illustrated by the enormous reduction 
observable in the gametophyte, and in the megaspore output, as 
we pass from homosporous to heterosporous forms. Economy is 
the keynote of the progress to heterospory, and of its outcome, the 
seed ; we shall endeavour to illustrate, from the series of Angio- 
sperms, that economy is also a guiding principle in the evolution 
of the flower. 
Our floral prototype, then, will be one in which the principle 
of economy is realized the least, and will therefore consist of an 
indefinite number of sporophylls, borne upon an axis more or less 
elongated, and repeating in their arrangement the succession of 
the vegetative leaves. Analogies are not far to seek ; they are 
common enough in the Gymnosperms; in the Firs, we find cones 
composed of an indefinite number of sporophylls arranged spirally 
like the vegetative leaves; in the Cupressineae, sporophylls and 
vegetative leaves are borne typically in decussating whorls. 
Perhaps the most striking analogy to this floral prototype is 
afforded by that interesting fossil group the Bennettiteas. The 
“ flower ” of Cycadeoidea ingens, figured by Wieland, and reproduced 
in Scott’s “ Studies,” p. 584, 1 consists, proceeding from below 
upwards, of an indefinite number of sterile bracts, followed by an 
equally indefinite number of complex frond-like male sporophylls; 
these are surmounted by the megasporangia, borne in large 
numbers upon the elongated continuation of the main axis. 
1 Second edition, 1910. 
