Pg E So E St eas Yea 
1878.] On the Natural Succession of the Dicotyledons. 733 
alous” do not properly designate the process by which these 
organs are developed. According to the accepted principles of 
phyllotaxy, each petal (as also each sepal) represents a transformed 
leaf; but the embryological study of those plants in which the 
corolla takes the form of a tube, has proved that this has not been 
produced by the union of the original petals, but by the forma- 
tion at first of a ring at their base which acquires greater promi- 
nence until it eventually assumes the character of a tube. To 
better indicate this process the terms “eleutheropetalous” and 
“ dialypetalous ” are employed by certain authors to denote that 
the petals are distinct, the term “ gamopetalous ” being used for 
the very objectional one “ monopetalous.” 
If natural selection has had anything to do with the develop- 
ment of these organs, it is certain that the free petals must have 
historically preceded the tube, and hence we may conclude that 
for the earliest forms of each division the order of succession 
was: first, Apetale; second, Lleutheropetale, and third, Gamo- 
petale, and therefore to whatever extent these divisions may now 
be parallel and coordinate, they were not so at the outset. 
If, therefore, we were to accord to the general principle of pro- 
tection, as above pointed out, its full force in the classification of 
dicotyledonous plants, at the same time keeping in view certain 
subordinate laws by which it is qualified, we should probably 
find, in attempting to reconstruct the present system, that while 
the so-called divisions would be virtually abolished and the orders 
within each very much blended and intermixed with those of the 
others, there would still remain an ascending series based on the 
perfection of the floral envelopes, and in which as now those 
-plants classed as apetalous would in the main stand at the base. 
The intermediate terms of this series would, however, unlike the 
present system, consist chiefly of those orders now placed in the 
polypetalous division, while the highest of these terms would be 
represented by the monopetalous orders with tubular corollas. 
This arrangement would be further modified by the relation of 
the calyx to the ovary and minor considerations. In fact, if the 
true genealogy of the Dicoty/@ is ever worked out it will doubt- 
less be found to conform to the general law in all departments of 
life, and to assume the arborescent form, whose ultimate ramifi-— 
cations it would be wholly sri sie to trace in-the present state | - 
of the science. 
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