on of the
various whorls, that may be traced in many plants, is a further proof of
concretion, rather than of expansion of the axis, but this argument may
fairly be met by the consideration that the several whorls emerge at
different heights.[558]

Organs originally free and distinct become ultimately combined at the
base by the gradual protrusion from the receptacle of a ring or tube
under them, as in the stamens of _Leguminosae_; yet, says Mr. Bentham, no
one would propose to describe the staminal tube of monadelphous
_Leguminosae_ as part of the receptacle and not of the stamens. Perhaps
not, for descriptive purposes, but morphologically it would not be easy
to separate such a tube from the receptacle. The principal kinds of
malformation which have a bearing on this subject are mentioned at pp.
77-81 and 247, from which it may be seen that the evidence furnished by
teratology is conflicting. It would seem, indeed, that while in some
families of plants there may be a real calyx-tube, in others the tubular
portion is a sheath-like prolongation of the axis. In _Primula_ or
_Pedicularis_, where the venation is clearly laminar, the tubular
portion is distinctly calycine. In other cases the so-called calyx-tube
seems as certainly to be an expansion of the receptacle, as in
_Rosaceae_, _Myrtaceae_, _Melastomaceae_, _Passiflora_,[559] &c.

Where the petals and stamens are described as being inserted into the
throat of the calyx, or are perigynous, it may be assumed as a general
rule, subject to but few exceptions, that the so-called calyx-tube is
really a portion of the receptacle.[560] After all, this is very much a
question of words, and for the following reasons,--very often the base
of the calyx does evidently form a tube, and no one can say where the
calyx ends and the receptacle begins. Again, many leaves are known to
originate in the form of a ring-like protrusion from the axis, and from
this primary ring originate secondary developments. Thus the asserted
difference between a leaf, with such a history of development, and an
axial structure becomes obliterated. From this point of view, peltate
leaves like those of _Tropaeolum_ or _Nelumbium_ become very significant.
In both the leaf-stalk is cylindrical and traversed, as in the case of
all cylindrical leaf-stalks, by a circle of fibro-vascular cords, as in
a branch, and which radiate in all directions in the blade of the leaf.
Now, if (as often happens to a slight ex