86 THE FLOWERING PLANT. 
of varying extent, and the free parts of the sepals, collectively 
forming the limb, usually appear in the margin of this as small 
pointed teeth or larger lobes. The general shape, when radially 
symmetrical, may be tubular, funnel-shaped, bell-shaped, inflated, 
&e. (cf. p. 89). The most common form of bilaterally symme- 
trical calyx is the labiate or lipped, where the free anterior and 
posterior portions form projecting lips. Dead nettle, sage, and 
gorse furnish examples. In all three cases there are five sepals, 
and in the first two the odd sepal is posterior, so that the upper 
or posterior lip is composed of three sepals, and the lower or 
anterior of two. Exactly the reverse is true of gorse. ‘The out- 
side of the gamosepalous calyx is often strongly ribbed, the ridges 
corresponding to the midribs of the united sepals. The gamo- 
sepalous calyx of Indian cress (garden nasturtium) possesses a 
large posterior spur. 
The surface of the calyx is very frequently provided with hair 
structures, especially on the outside, where prickles may also 
occur. More will be said about this in the sequel. 
Sepals are typically green in colour, but the brightly tinted or 
petaloid condition is very common, especially among monoco- 
tyledons, as snowdrop, tulip, lily, hyacinth, orchis, &e. Many 
dicotyledons also present examples of the same thing, e.g., many 
buttercups, larkspur, gorse, barberry. 
The texture of sepals varies considerably. They may be 
delicate, firm, membranous, or scaly. This has an influence on 
their duration, whether caducous (shed when the flower opens), 
deciduous (falling off when the seeds begin to ripen), or persistent 
(remaining during the ripening of the seeds). The last condition 
is especially characteristic of gamosepalous examples. 
Structure.—It need only be stated under this head that an 
ordinary green sepal resembles a foliage leaf, while a petaloid 
one is more or less like a petal (cf. pp. 64 and gt). 
The Corotua, in most dicotyledons at any rate, is the most 
brightly coloured part of the flower, and diverges more from the 
type of the foliage leaf than the calyx. 
Number and Arrangement.—The petals of an acyclic flower 
are generally indefinite in number, and not sharply marked off 
in character from the other floral leaves. Thus, in white water- 
lily, there is a gradual transition from sepals to petals, and from 
these again to stamens (fig. 39). Hemicyclic and cyclic flowers 
in dicotyledons generally possess five or four petals, while three 
is the usual number among monocotyledons. The same reasons 
may be given for this as in the case of the calyx (p. 83). Two 
petals sometimes occur (enchanter’s nightshade), and more rarely 
one, Many flowers possess no corolla at all, and in this case 
