ordinary
circumstances, as for instance the "obsolete" calyx of Umbellifers. In
the cauliflower the branches of the inflorescence are contracted in
length, while their succulence is much increased; at their extremities
they bear crowds of imperfect flowers, in which the calyx only is
visible, and that only in a rudimentary and partially developed
condition. Imperfect development of the whole or of some of the
constituent parts is more common in the case of the corolla than in that
of the calyx. In _Arenaria serpyllifolia_ the petals, especially in
autumn, are only one fourth the length of the sepals. _Anagallis
phoenicea_, _Honckenya peploides_, _Arabis alpina_, _Ranunculus
auricomus_, _Rubus fruticosus_, and _Geranium columbinum_, also
frequently afford illustrations of this circumstance.

[Illustration: FIG. 216.--Abortion of four out of five petals, _Viola
tricolor_, side and front views.]

At fig. 216 is represented a pansy in which four of the five petals were
very small and colourless, while the lower spurred petal was of the
usual size and colour. In this flower the stamens and pistils were
wholly suppressed, and the flower-stalk, instead of being bent near the
flower, retained its primary straight direction. Similar atrophic
conditions of the corolla occur habitually among _Violaceae_.

The diminished size of the petals sometimes coexists with an increase in
their number, as in a flower of _Streptocarpus Rexii_, mentioned by
Bureau.[530]

Among monocotyledons this partial development seems to be even more
frequent than in dicotyledons. In addition to the well-known cases of
certain species of _Bellevalia_ and _Muscari_, wherein the uppermost
flowers of the raceme are more or less atrophied (see p. 347, fig.
179), a few less common illustrations may be cited. In crocuses it is
not a very uncommon circumstance to find the three inner segments of the
perianth smaller than natural, and generally unequal in size. This
occurs without any other perceptible change in the flower.

Schlechtendal[531] mentions a flower of _Fritillaria imperialis_ in
which the perianthial leaves were relatively very small, and destitute
of the usual nectary, while the stamens, on the other hand, were of
their natural size and appearance. Fresenius[532] records a similar
occurrence in the same plant.

Morren[533] gives details of like appearances in _Hymenocallis
americana_, and Delavaud[534] in _Tigridia pavonia_.

In certain orchi