264 



STRUCTURE AND VITAL PROCESSES OF PLANTS 



Fig. 248. — MiisSctMHla frondosa. The 



large white leaf is one of the five 



lobes of the calyx. 



seen from a distance. If the corolla is inconspicuous, the 

 bracts may become coloured, as in Bougainvillea. In Mussanula 



{Kan. Bellotti: Mfl. Vellila) 

 ^C^ one calyx-lobe is much enlarged 



^^^ and looks like an ordinary leaf, 



but is white. Flowers that 

 open in the evening and must, 

 therefore, be pollinated by night- 

 moths, are generally white or 

 pale, so as to be easily seen in 

 the twilight (Jasmine, Crinum, 

 Clerodendron, Xyctanthes, etc.). 

 (ii) Inflorescences. — Large 

 flowers, as those of Hibiscus, can be discovered by visiting insects 

 even if they are single; but small Howers become conspicuous 

 only if tliey are grouped together in greater numbers. Such 

 a group of Howers is termed an intlorescence. The main axis 

 of the intlorescence is denoted peduncle, and the stalks supporting 

 the flowers pedicels. The leaves, from the axils of which the 

 pedicels issue, are smaller than the foliage leaves of that plant, 

 and are called bracts. The epicalyx of the Malvaceae (p. 13), 

 the involucre of the Compositre (p. 65), the spathe of the Palmea* 

 and Aroidecc (p. 140 and 147) and the glumes of the (iraminea> 

 (p. 173) are modifications or specialized forms of bracts. 



There arc a great many of various inflorescences, which, 

 however, can be referred mainly to two types. In one type, the 

 racemose or indefinite type, the main axis is stronger than any 

 of tlie side axes; in the other, the cymose or definite type, the 

 main axis is shorter and weaker than the side axis. Thus the 

 racemose infiorescence is a monopodium, and the cymose in- 

 fioresccnce a sympodium (see page 245). 



{aa) Racemose Inflorescences. — Here the princii)al axis goes 

 on elongating and gives off branches bearing Howers. The Howers 

 at the lower part of the peduncle are first developed and, there- 

 fore, open earlier than the upper ones. (Tliis is shown in the 

 illustrations by the various sizes of the circles denoting the 

 Howers.) 



