36 | ELEMENTARY BOTANY — 
The The corolla is generally the most conspicuous 
Corolla. part of the flower. Its colour is of great impor- 
tance in connection with the visits of insects to the flower. 
(See Chapter IX.) In many flowers the petals are similar 
to each other, as in the buttercup, wallflower, geranium; the 
flower is then said to be regular. In others, the petals 
differ from each other: one may form a spur which con- 
tains honey, as in the violet; or a petal may be specially 
developed to form a resting-place for the insect when it 
visits the flower, as the lower lip of the dead-nettle. Such 
corollas are described as irregular, and the irregularity is 
usually connected with insect, visits. Irregular corollas are 
described in connection with the Orders to which they belong, 
in Part IL. | 
The petals forming the corolla may be joined to each other, 
or they may be free. : 
The term perianth (Gk. peri, round; anthos, a 
flower) denotes the two outer whorls of floral 
leaves, which envelop the essential leaves, the stamens and 
carpels It is used in describing a flower, in which the calyx 
and corolla are very similar in appearance, either all petal-like, 
as in the snowdrop and hyacinth ; or all sepal-like, as in many 
flowers of trees. : 
The essential leaves of a flower, the stamens 
a and carpels, are sporophylls, 1.¢., spore-bearing 
and —_jeaves. A stamen consists of: (1) a stalk or fila- 
Gynecium. 
ment; (2) an anther. Stamens are usually free, 
not joincd to each other ; in the sweet pea and mallow the fila- 
ments are united, forming a tube, and in the daisy the anthers 
are united. The anther is attached to the filament in various 
ways. When the filament passes up between the two halves 
of the anther, as in the snowdrop, the anther is said to be adnate 
(Lat. ad, to ; nascor, to be born) ; when the anther is jointed at 
the bottom to the filament, it is innate, as in the wallflower. 
Some anthers, for example, those of the lily, are joined in the 
middle, and thus swing on their filaments, and the attachment 
of the anther is then described as versatile (Lat. verso, to turn). 
Perianth. 
