PHANEROGAMIA 



447 



Fig. 376. — A and B, anterior 

 and posterior view of a sta- 

 men of flyoscyamus niger ; 

 /, the filament ; p, anther ; 

 c, connective (magnified). 



Flowers unprovided with an enveloping perianth are termed 

 naked (achlamydeous) ; such are of rare occurrence among the Angio- 

 sperms (e.g. the Grasses, and Piperaceae). 



The andrcecium of most Angiosperms consists of filiform, 

 staminal leaves, the STAMENS, which bear no resemblance to ordinary 

 foliage-leaves. In each stamen there may usually be distinguished a 

 slender stalk-like portion, the filament, surmounted by an anther 

 containing four pollen-sacs. The anther gener- 

 ally consists of two swollen halves termed the 

 THECiE, parallel to the axis of the filament, and 

 each containing two pollen-sacs (Fig. 376). 



Each theca usually dehisces by a longi- 

 tudinal slit so situated along the partition walls 

 between the two pollen-sacs that it is common 

 to both (Fig. 358, A). In less frequent cases 

 the dehiscence of the anthers is effected by 

 means of pores or by openings with valves. 

 According to the position of the thecas, whether 

 on the inner (ventral) or outer (dorsal) side, the 

 anthers are designated respectively INTRORSE or 

 extrorse. 



The part of the anther uniting its two 

 thecse is termed the connective. It usually 

 consists merely of a thin plate of tissue (Fig. 376, C) ; sometimes, 

 however, it is more distinctively developed, as in Salvia (see Fig. 219), 

 where it is rod-shaped, projecting obliquely from the apex of the 

 filament, or as in the Violet and some of the Ericaceae, in which it 

 forms horn-like spurs. 



The pollen-grains are variously shaped, dry and smooth where 

 pollination is effected by the wind, but more or less sticky or spinous 

 when adapted for entomophilous pollination. In some cases they 

 cohere in tetrads or in larger groups (Fig. 359). 



The stamens, although generally quite free from each other, are 

 sometimes coherent into several bundles, as in Hypericum; or, as in 

 Ononis, into a tube, or into a column, as in the case of Cucurbita. The 

 cohesion may extend throughout their whole length (e.g. Cucurbita), or 

 it may be restricted to the filaments (e.g. Malvaceae). 



By the branching of the stamens an appearance is produced 

 similar to that resulting from their fusion. It is often only possible to 

 determine which may be the case by a comparative study of their 

 mode of development in allied forms. Sometimes the branched char- 

 acter of the stamens is indicated by the fact that the anthers 

 each contain only one theca, and appear to be halved. Undoubted 

 examples of branching are afforded, for instance, by the flowers of 

 Bicinus, with tree-like, branching stamens, or by those of the Malvaceae, 

 in which the stamens are coherent below and branched above (Fig. 377). 



