Chapter 4 



THE ANDROECIUM 



Classification by Arrangement on the Receptacle 



The aggregate of the stamens of a flower constitutes the androecium. 

 In number, the stamens of a flower range from many to one, from in- 

 definite to definite. In arrangement on the receptacle, they are spiral, 

 whoiied, or fasciculate (clustered) — the fascicles usually in whorls. 



The Spiral Androecium. Many stamens, spirally arranged, constitute 

 the primitive androecium, from which have been derived the whorled 

 and the fasciculate types. This androecium is present in many of the 

 lower dicotyledons — Degeneriaceae, Dilleniaceae, Magnoliaceae, Eupo- 

 matiaceae, Annonaceae, Calycanthaceae, Nymphaeaceae, and some of 

 the Ranunculaceae, Monimiaceae, and Winteraceae. 



The Fasciculate Androecium. The nature of stamen fascicles was much 

 discussed — with little agreement — in the earlier days of taxonomic 

 morphology. It has recently received attention again, chiefly in connec- 

 tion with the theory of the telomic structure of the stamen. The fascicle 

 has been considered both a branching and a compound organ: its 

 branching, the result of radial and tangential splitting (chorisis) of a 

 simple stamen; its compound nature, the result of aggregation of simple 

 stamens, connate in various degrees (Fig. 43). Fascicles consist of 

 various numbers of stamens — from very many, to few, and to one. 

 Within the fascicle, development is often, perhaps always centrifugal. 

 Connation is of various degrees — by the stamen traces within the re- 

 ceptacle and, externally, by the filaments. Stages in the connation are 

 present in several families — Dilleniaceae, Paeoniaceae, Cactaceae. In 

 these families, a few stamens in the cluster may be wholly free, both 

 externally and in their traces. Ontogeny, in showing fascicles arising as 

 a mound, with individual stamens developing on the surface, has been 

 considered to show evidence of branching. But evidence from ontogeny 

 is not in itself conclusive; organs phylogenetically fused arise con- 

 genitally united, wholly or in part. A comparable condition exists in 

 the sympetalous corolla where the lobes — morphologically, the petal 

 tips — and the tubular base arise from a simple primordium. 



The fascicle has been interpreted as a primitive form of the stamen, 

 a branching system of fertile telomes, reduced and compacted, with the 



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