256 



PLANT LIFE. 



cross-pollination, the agency of wind or water or insects is 

 employed. To the peculiarities of these various agents, 

 flowers adapt themselves in character of pollen, color, nectar, 

 odor, form of parts, time of development of stamens and 

 stigma, etc. For an account of these see ^% 477-482. 

 359. Bracts. — In the immediate neighborhood of the 

 perianth the leaves are usually modi- 

 fied at least in form and size, and 

 not infrequently in color. The 

 leaves in whose axils the flowers 

 arise are called bracts, as are also 

 those which subtend branches of the 

 inflorescence (h\ ft*, h 3 , fig. 139). 

 The axis of the flower, when 

 elongated beneath it, usually bears 

 one or more bractlets. 



The bract is sometimes large and 

 surrounds the entire inflorescence, 

 as in Indian turnip (fig. 279) and 

 the calla, when it may be vari- 

 ously colored. Highly colored 

 bracts occur in the scarlet sage 



Fig. 279.— Inflorescence of Indian and, with inCOnspicUOUS flowers, 

 turnip (a spadix), surrounded . . 



by a large striped and mottled in poinsettia and painted CUp, 

 bract, the spathe. Natural size. 



—After Gray. while the four large whitish bracts 



of dogwood are the only conspicuous part of the inflores- 

 cence (fig. 280). 



Bracts are, aggregated to form an involucre beneath a head 

 (If 104), as in the sunflower family (figs. 281, 409), or an 

 umbel (^[ 104), as in the parsnip. The perianth may be 

 almost or quite wanting, and the bracts and bractlets may 

 be the only protective leaves for the sporophylls, as in the 



generally its final result, the terms close- or self-fertilization and cross- 

 fertilization were formerly used. The word pollination is preferable. 



