168 MANUAL OF BOTANY 



c. The Andrcecium. 



The androecium is the whorl or whorls of sporophylls which, 

 in a complete flower, is situated between the corolla or peri- 

 anth on the outside, and the gynoeoium on the inside ; it 

 is placed between the calyx and gynnecium when the corolla 

 is absent [fig. 255), as in nionochlamydeous flowers; in 

 achlamydeous flowers, it is either outside the gyncecium (fig. 



256) when those flowers are bisexual, or it stands alone (fi^. 



257) when the flowers are unisexual and staminate. These 

 leaves or sporophylls, which bear the microsporangia, are termed 

 stamens. Each stamen is generally composed of a thread-like 

 portion or stalk, called %\ie filament {fig. 334,/) ; and of a club- 

 shaped head, a, called the antlier; this consists of a sorus of 



four microsporangia or pollen-sacs, which con- 

 ■ ' ' ' tain the microspores or pollen-grains. It not 

 unfrequently happens that flowers contain sterile 

 filaments, that is, filaments without anthers, 

 in which case these structures are termed 

 staminodes. They commonly present a flat- 

 tened appearance, as in the flowers of the 

 Fig. 330. stamen speoies of Conna. When, as is rarely the case, 

 pint (Armn ma- ^^^ filament is absent, as in the Cuckoo-pint 

 cuiatum), con- (/jff, 330), the anther is described as sessi?c. 

 sistmg simply of mi, i, iv. • • n 



an anther which Thoiigh the microsporangia are usually 



thettoiam "''°" bome upon sporophylls (stamens), this is 



not without exception. In some aquatic 



plants, such as the Naiadacese, and in some tropical trees, they 



occur upon certain portions of the axis. When this is the case, 



the term stamen is still applied to the structure bearing them. 



Before discussing the androecium as a whole it will be well 

 to examine the peculiarities of the stamens of which it is com- 

 posed. Each consists, as we have seen, of a filament and an 

 anther. 



1. The Filament. — The filament varies in form, length, 

 colour, and other particulars ; a few of its more important 

 modifications will be now alluded to. 



Form. — As its name implies, the filament is usually found 

 in the form of a little thread-like or cylindrical prolongation 

 which generally tapers in an almost imperceptible manner from 

 the base to the apex, when it is described as filiform, as in the 

 Rose ; or if it is verj- slender, as in most Sedges and Grasses, it 



