86 THE FLOWERING PLANT. 



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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, 

 &c. (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, &c. 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. 



The Corolla, 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 charneter 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. S3). Two 

 petals sometimes occur (enchanter's nightshade), and more rarely 

 one. Many flowers possess no corolla at all, and in this case 



