Ficaria verna , and other Members of the Ranunculaceae . 53 
In any consideration of the Ranunculaceous perianth the construction 
which it primitively exhibited is necessarily important, and Erantkis sheds 
some light on this question. Two conditions are found in Ranunculaceae, 
viz. the pentamerous and the trimerous, and both are met with in the present 
species, though the former condition but rarely. As already stated, in most 
cases where there are only five coloured perianth segments this is due to 
the transformation of one ; but rarely a true pentamerous perianth is found, 
and where such is the case the five members exhibit a quincuncial arrange- 
ment as in typical pentamerous species. It is clear that this condition can 
easily have been derived from two alternating whorls of three members 
each if we assume that the member which is half external, half internal, was 
formed by the fusion of the anterior member of the outer perianth with one 
Fig. 5. Eranthis hyemolis. a and b, lobed perianth segments; c, trilobed bract replacing 
a perianth member; d, partially virescent perianth segment; e-g, lobed perianth segments; 
H, partially coloured bract ; I, supernumerary perianth segment. Green parts indicated by shading. 
or other of the lateral members of the inner perianth, according as the flower 
exhibits a right-handed or left-handed spiral. This would produce the typical 
quincuncial imbrication. That the perianth member in question has been so 
derived would seem to be indicated by the fact that in some cases it exhibits 
six principal veins in place of the usual three. The anterior perianth segment 
in a quincuncial flower may, moreover, be bilobed, and its attachment is 
broader than that of the other segments. In Eranthis there can be no 
question that the pentamerous condition has been derived from the trimer- 
ous, and in view of the widespread character of the latter type in related 
families it may well have been the primitive condition in the Ranales as 
a whole. Thus we find that in the Nymphaeaceae the genera with the 
least specialized type of ovary, viz. Cabomba and Brasenia , are trimerous 
