THE ANDROECIUM 105 



There is great variety in the form and function of sterile modified 

 stamens: they may be transformed into petaloid organs — Eupomatia, 

 TroUhis; or into secretory organs — Coptis. Frequently they are repre- 

 sented by abortive structures, mere stubs, or vascular traces ending in 

 the receptacle — Scrophulariaceae, Anacardiaceae. Reduction to one fer- 

 tile stamen and the sterilization of half the anther of that stamen, with 

 the sterile part petaloid, are characteristic of some highly zygomorphic 

 families — Cannaceae, Zingiberaceae, Marantaceae, some Aizoaceae. 



Reduction of Stamen Fascicles. The formation of fascicles is probably 

 an early step in androecium reduction. Further steps consist of reduc- 

 tion in number of fascicles and in number of stamens per fascicle. Both 

 these steps are well shown in Hibbertw, where reduction of fascicles is 

 from several to one, and of stamens, similarly, from many to very few; 

 and in Hypericum, where five fascicles are reduced to three, and sta- 

 mens per fascicle from many to about three. Extreme reduction in the 

 fascicle is seen in the Lauraceae and in Tarnass'm; some apparently 

 simple stamens are surviving members of reduced fascicles — those of 

 Sassafras, Benzoin. 



Fusion in the Androecium 



Connation of members of a whorl — ontogenetic or phylogenetic — is 

 frequent in both whorled and fasciculate androecia. An androecium 

 with connation by filaments is monadelphous where all stamens form a 

 single cluster; diodeJphous where two clusters are formed; polijadeJphous 

 where there are more than two clusters. It is adelphous where there is 

 no connation. An androecium with anthers united is termed syngenes- 

 ious. Union of anthers is commonly ontogenetic but is congenital in 

 some taxa. Ontogenetic fusion commonly covers cohesion as well as 

 connation. (Cohesion implies a loose, not intimate, union of similar 

 structures, brought about by glandular secretions, by close appression 

 with interlocking of epidermal cells, or by cuticular projections; conna- 

 tion implies histological union, with lines of union either evident or 

 obscure. The anthers of the Compositae, Lobeliaceae, Solanaceae, some 

 Gentianaceae are coherent.) Connate anthers are infrequent or rare^ 

 the Typhaceae, some Cucurbitaceae. The anthers of the Lobelioideae 

 seem to show stages from cohesion to connation. Fusion by filaments — 

 monadelphous or diadelphous — may involve one, two, or perhaps more 

 whorls. Union of two whorls to form an apparent one is frequent, as 

 in some legumes and the Thymelaeaceae. 



Adnation of the Androecium 



Fusion of stamens to other organs of the flower, especially to the 

 corolla (this is termed epipetaly), is common. Fusion to the calyx is 



