470 



PHANEROGAMS. 



of small green leaves, as in the Chenopodiacece and Urticaceae, but is sometimes 

 large, of delicate structure and brightly coloured (petaloid), as in Aristolochia, 

 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 Ca/jx 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 



Fig. 330. — Hippiiris vulgaris ; A piece ot an erect stem, the flowers standing in the axils of tlie whorl of leaves (which have 

 been cut off) ; B horizontal section of a female flower above the ovary, p perianth, cp carpel ; C horizontal section of the anther ; 

 I— IV longitudinal section of flowers in various stages of development, a anther, f filasnent, g: style, n stigma, / perianth, 

 fk the inferior ovary, sk the pendulous and anatropous ovule. • 



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- 

 cacese, or both petaloid, as in Lilium; in Helleborus, Aconitum, 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. Opuntia), or they may all be petaloid (as in Epiphyllum 



' The substantives caljTc and corolla then designate the position of the whorl, the adjectives 

 sepaloid and petaloid the nature of the part. 



