ANGIOSPERM^E 



351 



conspicuously colored, and together form the Corolla. Within the 

 corolla are the stamens, upon which are borne the pollen-sacs. The 

 stamen is usually differentiated into a stalk (Filament) and the Anther, 

 which is made up of the microsporangia, or pollen-sacs. Collectively, 

 the stamens form the Androscium. The innermost sporophylls, 

 the carpels, may be separate, 

 but more commonly they are 

 united to form a compound 

 Pistil. Collectively, the car- 

 pels constitute the Gynae- 

 cium. The typical pistil 

 shows three portions, the basal 

 Ovary, within which are borne 

 the ovules; the intermediate 

 Style, and the terminal 

 Stigma, upon which the pol- 

 len-spores are deposited. The 

 stigma has usually a papillate 

 surface, with a viscid secre- 

 tion, which serves both to hold 

 the pollen and to induce its 

 germination. 



Development of the Flower 



The development of the typi- 

 cal flower follows closely that 

 of a vegetative shoot. The 

 receptacle corresponds to the 

 growing-point of the shoot, and 

 about this are produced the 

 various floral leaves in precisely 

 the same way that the foliage 

 leaves arise from a vegetative 

 shoot (Fig. 316). The sepals 

 are first to develop, commonly 

 followed by the stamens, the 



o [ 



FIG. 315. A, Calochortus venustus, stamen, 

 showing filament, /, and anther, an. B, 

 Chimaphila maculata, stamen opening 

 by terminal pores. C, " diadelphous " 

 stamens of Pea; car, pistil. 1), Arisasma 

 triphyllum, section of the ovary, showing 

 the erect, basal ovules, ov. E, Reseda 

 odorata, cross-section of ovule, showing 

 the three carpels and parietal ovules. 

 F, Epilobium spicatum, ovary composed 

 of four carpels, ovules axial. G, Bro- 

 diaea capitata, pistil, showing ovary, o, 

 style, gr, and stigma, st. 



petals not infrequently becoming evident at a later period. 



The ovary may arise as a continuous wall about the apex of the 

 floral axis, or the separate carpels may be evident from the first. 

 Usually the formation of the gynaecium stops the further growth in 

 length of the floral axis. 



The Sporangia and Gametophytes 



The stamen is in most cases a true foliar organ, but exceptionally 

 e.g. Naias it is a direct development of an axis, and the anther 



