502 



HOT ANN 



OF ANGIOSPERMS, although these features do not apply without 

 exceptions to all angiospermic flowers. These differences depend 

 on the important factor of the MEANS OF POLLINATION. When, 

 as is the case with the Gymnosperms and the catkinate flowers 



of Angiosperms, this func- 

 NN tion is performed by the 



^ wind, the elongation of the 



axis and the absence of an 

 investment of leaves around 



Fio. 470. Flower of J'ueonia peregrina, in longitudinal 

 section, k and c, Perianth ; a, androecium ; g, gyn- 

 aecetim. (J nat. si/t>.) 



Kn.. 471. Flourr ol A'-urus Calamus, 

 pg, pprigont- : c, androecinn; : g, 

 ji.vnaeceum. (Enlanj"*!. Att'-r 

 ENOLER.) 



f- 



the female receptive organ are advantageous. When, on the other hand, 

 pollination is effected by insects or birds, the conspicuousness given 

 by the presence of a perianth and other attractions, such as scent or 

 sweet-tasting substances, are necessary. The form of the flower, the 

 arrangement of the sporophylls in it, and the 

 place at which nectar is secreted must be 

 adapted to the visiting insects (cf. p. 308). 

 It is to this, that the variety of form arid colour 

 exhibited in the flowers of Angiosperms must be 

 ascribed. According to the means of pollina- 

 tion, anemophilous, entomophilous, ornithophil- 

 ous etc. flowers are distinguished. 



The perianth (Figs. 470, 471) consists of 

 two whorls of members : these may be similar 

 in form and colour, when the name PERIGOM: 

 is given to them, or may be differentiated into 



FII;. 472. .4 and B, anterior & j u i r 



and postal ior view of a sta- an outer green CALYX and an inner whorl or 



men of Hyostyaihiis niger ; coloured leaves, the COROLLA. In every COD1- 



/, the filament ; p, anther ; p] ete fl ow er two whorls of stamens or micro- 



c, connective (magnili.-d). , , , 



sporophylls come next within the perianth, and 



within these again a whorl of carpels or macrosporphylls. The whorls 

 alternate regularly with one another. The stamens collectively form 

 the ANDROECIUM, the carpels the GYNAECEUM. 



Each stamen consists of a cylindrical stalk or FILAMENT and of 

 the ANTHER ; the latter is formed of two THEC^E or pairs of pollen- 



