THE STAMEN 131 



"Dichotomous" stamens have been seen as occurring in Salix in the in- 

 terpretations of the "New Morphology," as examples of retention of 

 primitive structure. The "dichotomous" stamens of some species of 

 this genus are pairs of stamens partly united, not forked organs. Two 

 stamens borne on opposite sides of the flower and connate by the 

 bases of their filaments may suggest dichotomy, but anatomy of the 

 flower shows two independent vascular supplies, derived on opposite 

 sides of the receptacle. Taxonomists have correctly interpreted this 

 "doubled" stamen as an end product of reduction in the androecium. 



Dedoublement, a doubling — if repeated, a multiplication — of stamens 

 has, since the middle of the nineteenth century, been used in both 

 taxonomy and morphology to explain the presence of two — sometimes 

 more than two — stamens, where one would be expected in a floral 

 pattern (Fig. 48). Among the best known examples of supposed de- 

 doublement are the pairs of longer stamens in the Cruciferae and the 

 pairs of stamens opposite each petal in Alisma. In the crucifer flower, 

 two pairs of stamens would fit into the dimerous floral diagram of the 

 family, with two pairs (whorls) of sepals, two of petals, and two of 

 carpels. But six stamens cannot be placed in alternating whorls of two 

 with the other organs. Dedoublement of two of an original four (two 

 whorls) has been used to explain this lack of conformity in the 

 androecium. Neither anatomy nor ontogeny supports the doubling 

 theory; the vascular supply and the primordia of all the stamens arise 

 independently. The members of each pair of stamens in Alisma repre- 

 sent independent organs with their vascular supplies derived well apart 

 on the floral stele. 



Many objections were raised at the end of the nineteenth century to 

 the acceptance of dedoublement as an explanation of the presence of 

 pairs and clusters of stamens where a single organ is to be expected. 

 Fifty years later, dedoublement, in the sense of a division, seems to be 

 a sound explanation of the origin of those pairs or clusters of "half- 

 anthers" where it is obvious, on anatomical and ontogenetic evidence, 

 that the anthers have been divided longitudinally. In these stamens, the 

 division may extend downward in the filament even to the base — some 

 of the Malvales. But its use as an explanation of pairs of complete 

 stamens, with independent vascular supplies is morphologically in- 

 correct. 



Forked stamens, apparently the result of longitudinal division or 

 "splitting," are occasional, as in Salix, Corijlus, and Ostnja, but these 

 stamens represent pairs of stamens connate throughout part of their 

 length, rather than forked individual organs. Dedoublement, as a true 

 splitting, a dividing of the entire stamen, has been claimed for Adoxa, 

 where pairs of stamens alternate with the petals, with separation oc- 



