OF PERIANTH, BTC. 461 
extremities they bear crowds of imperfect flowers, in 
which the calyx only is visible, and that only in a rudi- 
mentary and partially developed condition. Imperfect 
development of the whole or of some of the constituent 
parts 1s more common in the case of the corolla than in 

Fie. 216.—Abortion of four out of five petals, Viola tricolor, side and 
front views. 
that of the calyx. In Arenaria serpyllifolia the petals, 
especially in autumn, are only one fourth the length of 
the sepals. Anagallis phenicea, Honckenya peploides, 
Arabis alpina, Ranunculus auricomus, Rubus fruticosus, 
and Geraniwm columbinum, also frequently afford illus- 
trations of this circumstance. 
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 habit- 
ually among Violacee. 
The diminished size of the petals sometimes coexists 
with an increase in their number, as in a flower of 
Streptocarpus Rewti, mentioned by Bureau.* 
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 
1 * Bull. Soc. Bot. France,’ vol. viii, 1861, p. 710. 
