THE ESSENTIAL OKGANS STAMENS. 119 



The simplest state is that of one or more glandular papillae upon the recep- 

 tacle, as in the Cruciferse. In the Crassulacese (Sedum, 

 Sempervivum) we find a circle of glandular bodies Fig. 222. 



outside the carpels and between these and the 

 stamens. In Cobcea, the Vine, and other flowers 

 there is a five-lobed hypogynous disk, the stamens 

 being inserted outside or between the lobes. In 

 Citrus (fig. 222) the disk forms a perfect ring round 

 the ovary. In Gaultheria there is a double circle of 

 scales between the stamens and the ovary. On the 

 other hand, in Tinea there are two glands, alter- 

 nating with the two carpels of the ovary. The 9-tudy 

 of these structures is very interesting in regard to the Fi ower O f curus with the 

 reduction of irregular flowers to regular types. Some petals and stamens re- 

 of the structures are rudimentary petals or stamens ; ^y^and^the 1 alnular 

 and in other cases they are referable to developments disk surrounding the 

 of the receptacle or torus itself (p. 100). ovary, in this case the 



disk is an outgrowth 

 from the receptacle. 



The Androecium. 



The Stamens taken collectively form the Andreecium. The 

 essential character of a stamen is, that it is that organ in which 

 are formed the pollen-grains, the bodies by means of which the 

 fertilization of the ovules is effected. A completely developed 

 stamen (fig. 223) exhibits two principal regions, the filament or 

 stalk (a), corresponding to the petiole of a leaf, or, as Clos thinks, 

 to the midrib of: a petal ; and the anther (6), corresponding to the 

 blade of a leaf. The anther is a hollow case containing pollen, and 

 is therefore the only essential part of the organ : the filament may 

 be wanting or merely rudimentary ; and the anther then remains 

 sessile, like a leaf-blade when the petiole is not developed. The 

 normal position of the stamens is between the petals and the pistil ; 

 each stamen, under ordinary circumstances, intervenes between 

 two petals or is alternate with them, and therefore superposed or 

 opposite to a sepal. In Naias and Typha it is supposed that the 

 stamen is axial and not foliar. 



The base of the filament, or of the so-called sessile anther, is usually 

 articulated to the receptacle when these organs are free ; but this con- 

 dition is more or less disguised when the stamens are adherent to or inse- 

 parate from the calyx, corolla, or ovary. 



Staminodes or sterile filaments, i. e. such as are devoid of 

 anthers, occur in many flowers in regular circles ; and not unfre- 

 quently one or more stamens exist in this condition in un- 

 symmetrical flowers. Sometimes these staminodia are reduced to 

 mere scales, as in the odd stamen of Scrophularia (fig. 224), or to 

 glandular papillaB, as in the flowers of many Cruciferse. 



