166 



BRACTS OB FLORAL LEAVES. 



the base of the peduncles, but more usually they are deciduous, falling 

 off early by an articulation. In some instances they form part of the 

 fruit, becoming incorporated with other 

 organs. Thus, the cones of Firs (fig. 201) 

 and the strobili of the Hop, are composed 

 of a series of bracts arranged in a spiral 

 manner, and covering fertile flowers ; and 

 the scales on the fruit of the Pine-apple 

 (fig. 256 a), are of the same nature. In 

 Amenta or catkins (fig. 238), the bracts 

 are called squamce or scales. As regards 

 their arrangement, they follow the same 

 law as leaves ; being alternate, opposite, or 

 verticillate. 



347. At the base of the general umbel 

 in umbelliferous plants, a whorl of bracts 

 often exists called a general involucre (fig. 

 241 i f ), and at the base of the smaller umbels 

 or umbellules, there is a similar leafy whorl 

 called involuceloT partial involucre (fig. 241 i"). 

 In the case of Composite, the name involucre 

 is also applied to the leaves or scales surrounding the head of flowers (fig. 

 242 J), as in Dandelion, Daisy, and Artichoke. This involucre is often 

 composed of several rows of leaflets, which are either of the same or dif- 

 ferent forms and lengths, and often lie over each other in an imbricated 

 manner. When the bracts are arranged in two rows, and the outer row 

 is perceptibly smaller than the inner, the involucre is sometimes said 

 to be caliculate as in Senecio. The leaves of the involucre are spiny in 

 Thistles and in Dipsacus (fig. 244 e z), and hooked in Burdock. Such 

 whorled or verticillate bracts may either remain 

 separate (polyphyllotis), or be united by adhesion 

 (gamophyllotis), as in many species of Bupleurum, 

 and in Lavatera. In the acorn they form the cupula 

 or cup (fig. 257 c), and they also form the husky 

 covering of the Hazel-nut. 



348. When bracts become united together, and 

 overlie each other in several rows, it often happens 

 that the outer ones do not produce flowers or be- 

 come empty or sterile. In the artichoke, the outer 

 imbricated scales or bracts are in this condition, 



Fig. 256. Fruit of Pine-apple (Ananatsa satira), composed of numerous flowers united into one 

 mass; the scales, a, being modified bracts or floral leaves. The crown, b, consists of a prolonga- 

 tion of the axis bearing leaves, which may be considered as a series of empty bracts, i. e. bracts 

 not producing flowers in their axil. 



Fig. 257. Acorn, or Fruit of the Oak. f, Cupula or cup, formed by the union of numerous 

 bracts or floral leaves, the free points of which are seen arranged in a spiral manner. 



