518 PART III. THE CLASSIFICATION OF PLANTS. 



stamens, that is to say the filaments, branch; either, like most 

 leaves in a plane perpendicular to the median plane, as in Myr- 

 tacege and FumariaceaB, or in various planes, as in Ricinus (Fig. 

 333) and Hypericacea? ; an anther is borne on each of the branches 

 of the filament. 



Somewhat similar in appearance, but essentially different in 

 structure, are the coherent stamens of the PapilioneaB and other 

 plants. The stamens of each flower may be coherent into one or 

 more bundles. The arrangement becomes complicated when the 

 filaments are at the same time coherent and branched as in the 

 Malvacea?. When the filaments are all coherent into a single 

 bundle (e.g. Malvaceae), they are said to be monadelphous : when 

 in two bundles (e.g. some Papilioneae, Fumariaceee), they are 

 diadelphous ', when in several bundles (e.g. Hypericacese), they are 

 polyadelphous. In the Composite (e.g. Sunflower and Thistle), 

 though the filaments are free, the anthers become coherent or 

 syngenesious. When the stamens are quite free from each other 

 they are said to be polyandrous. 



A variety of the monadelphous condition is found in the $ flowers of 

 certain Araceae, where the stamens are united into a central column termed a 

 synandrium. 



Besides these varieties of cohesion, adhesion frequently occurs ; 

 that is the filaments adhere to other portions of the flower, par- 

 ticularly of the perianth, so that they or when they are very 

 short, the anthers appear to be inserted not upon the axis of 

 the flower, but upon the leaves of the perianth (epipetalous or 

 epipliyllous) . This condition is most frequently present when the 

 petals themselves are connate and form a tubular corolla, e.g. 

 Primula. The adhesion of the stamens to the carpels is of rarer 

 occurrence (e.g. Orchidaceae, Stylidium, and Aristolochia) ; the 

 flower is then termed gynandrous. 



In many flowers it happens that certain filaments, occupying a 

 definite position with regard to the other parts of the flower, are 

 longer than the others ; thus, of the six stamens of the Cruciferae 

 (e.g. Wallflower and Cabbage), four are much longer than the other 

 two; of the four stamens of the Labiatae (e.g. Lamium), two are 

 longer than the other two. In the former case the stamens are 

 said to be tetradynamous, in the latter didynamous. 



Stamens which bear no anthers are termed staminodia : they 

 are to be found in flowers which have become monosporangiate 



