50 MESSRS. NEWELL ARBER AND J. PARKIN ON 
the many-leaved floral envelope of Trollius, with its spirally arranged and 
largely petaloid members, as a primitive perianth. 
Without going into further details as regards the Ranales, we believe 
their perianth can be best explained on the assumption that their ancestors 
possessed one composed of an indefinite number of members spirally arranged, 
of which the outer were sepaloid and the inner petaloid, but with no marked 
separation between the two. Since we regard the Ranales as the most 
primitive group, we should expect the immediate ancestors of the Angiosperms, 
as a whole, to have possessed this type of perianth. 
Without attempting to follow fully the evolution of the perianth in the 
higher cohorts of the Dicotyledons, a few tentative remarks here may not be 
out of place. It might be inferred from the above hypothesis of а primitive 
perianth, partly sepaloid and partly petaloid, that we would consequently 
derive the floral envelopes of the higher Polypetale and the Gamopetale by 
a marked separation of the sepaloid and petaloid members into two distinct, 
usually pentamerous whorls, corresponding respectively to the calyx and 
corolla of these sub-classes. This of course is a possible, and besides a 
simple view, but there may be other explanations, which appear equally 
plausible. А.Р. De Candolle long ago suggested that all floral leaves are 
derived from the sterilisation of sporophylls. Celakovsky *, from an exhaustive 
study of the perianth, finally came to the same conclusion. For the petals, 
at any rate, this view is supported by the Ranunculacez, where the evolution 
of a “corolla” of honey-leaves, by a modification of stamens, can be traced. 
A third origin of the biseriate perianth occurs to us, on the supposition of 
a primitive floral envelope. The latter may have become wholly petaloid, and 
persisted as the corolla, whereas the calyx may have been a new structure, 
derived from foliage leaves. 
In the Ranales we believe it is possible to trace the origin of a double 
perianth in conformity with each of these three theories. As regards the 
first method—viz., the differentiation of the original simple perianth into 
a definite calyx and corolla,—the flowers of Drimys, and of members of the 
Anonaceæ, may be instanced. As regards the second, the direct origin of 
the corolla from stamens may be followed in Ranunculus; and with respect 
to the third—viz., a calyx derived from below through a modification of 
foliage leaves, or, their direct homologues, bracts,—attention may be drawn 
to Anemone Hepatica, Linn., Реота, and genera of ОШешасез f. 
In fact, the Ranales may be considered an experimental group so far as 
the formation of a distinct calyx and corolla is concerned, some members 
progressing in one direction, and some in another. 
* Celakovsky (1897) Part II. p. 46. 
1 Placed in the Cohort Ranales by Bentham and Hooker. 
