53« 
PHANEROGAMS. 
frequently partially obscured at a subsequent period by bilateral development and 
abortion. 
The Floral Envelope or Perianth is only rarely entirely wanting, as in the 
Piperaceae and many Aroideas ; more often it is simple, i. e. it consists of only 
one whorl of two, three, four, five, or rarely a larger number of leaves (as in 
Figs. 357, 358); in this case the perianth is frequently inconspicuous and composed 
of small green leaves, as in the Chenopodiacese and Urticaceae, but is sometimes 
large, of delicate structure and brightly coloured (petaloid), as in Arislolochia, 
Mirabilis, &c. But in both classes of Angiosperms (Monocotyledons and Dicoty- 
ledons) the perianth is usually composed of two alternating whorls consisting of the 
same number of leaves, two, three, four, five, or rarely more. In most Dicotyledons 
and many Monocotyledons the form and structure of these two whorls is very 
different ; the outer whorl or Calyx consisting of stouter, green, usually smaller leaves 
(^Sepals), while the inner whorl or Corolla is more delicate, and is formed of white or 
bright-coloured, usually larger leaves [Petals). It is however more convenient, for 
the sake of brevity, as Payer has already suggested, to designate the inner whorl as 
corolla, the outer whorl as calyx, even in those cases where the structure of the two 
is the same ^ ; and this is the more necessary since the contrast of structure 
referred to is frequently wanting, both whorls being either sepaloid, as in Jun- 
caceae, or both petaloid, as in Lilium ; in Helleborus, Aconiiwn, and some other 
species, the outer whorl or calyx alone is petaloid, the inner whorl or corolla 
being transformed into nectaries. In some Dicotyledons the perianth does not 
consist of alternating whorls, but of a smaller or larger number of turns of spirally 
arranged leaves, the number of which is then usually large or indefinite ; the outer 
or lower leaves of this spiral arrangement may in this case also be sepaloid, the inner 
ones alone petaloid {e.g. Opuntta), or they may all be petaloid (as in Epiphyllum 
and Trollius), or a gradual transition takes place from the sepaloid through the 
petaloid to the staminal structure (as in Nymphcßd). 
But besides the usual sepaloid and petaloid form and structure of the perianth- 
leaves, there occur other considerable deviations from the ordinary foliar structure. 
Thus, for example, the (imperfect) perianth of Grasses consists of very small delicate 
colourless membranous scales (the Lodtcules), that of some Cyperaceae is replaced by 
hair-like bristles, the Setce ; in the place of the calyx of Composite a crown of 
hairs, the Pappus, surrounds the corolla ; and it has already been mentioned that the 
petals of Aconitum J Helleborus, &c. are transformed into nectaries of a peculiar 
form. 
Whether the perianth consist of one or two whorls, the leaves of the same 
whorl have very commonly the appearance of being coherent or of coalescing with 
one another, forming a cup, bell, tube, and so forth, the number of the coherent 
sepals or petals being determined by that of the marginal teeth. Coherent perianth- 
whorls are produced, after the formation of the distinct foliar structures at the cir- 
cumference of the receptacle, by the common zone of insertion of these distinct 
structures being raised up by intercalary growth as an annular wall, and forming, as 
^ The substantives calyx and corolla then designate the position of the whorl, the adjectives 
sepaloid and petaloid the nature of the part. 
