THE STAMEN 151 



smaller than the inner, a character that is so deep-seated that it is 

 present in most highly specialized anthers. 



The vascular structure of stamens, as a whole, gives no support to 

 the hypothesis of telome structure in the stamen; no vascular tips lead 

 to or directly toward the individual sporangia. (Vascular branches are 

 frequent in the connective of some taxa but rarely penetrate the wall 

 between members of the pairs.) 



The stamen of Ricinus has often been cited as an example of solitary 

 sporangia terminal on dichotomizing branches of the stamen, but the 

 position of these sporangia is now better understood. The anther in 

 this genus has remarkable form; the connective is scalelike, subtending 

 the stalked unisporangiate anther lobes (Fig. 44). 



The telomic theory has been considered to aid in the interpretation 

 of stamen fascicles with their complex structure; under this theory, the 

 fascicle can be interpreted as a compacted system of telomes. But, in 

 the vascular system of a fascicle, there is no evidence of dichotomy. 

 And comparative anatomical study of fascicles in several families, espe- 

 cially in the Dilleniaceae and Paeoniaceae, shows that the fascicle is an 

 aggregation of simple stamens (Fig. 46). 



Staminodia 



Staminodia are sterile floral organs that apparently represent stamens 

 morphologically, resembling them more or less in form and closely in 

 relation to the receptacle and to other floral organs. They have great 

 variety of form. In most angiosperms, the petals are, morphologically, 

 elaborated, sterile stamens and could well be called staminodia. Some 

 taxa have staminodia which are transitional in form and loss of fer- 

 tility from stamen to petal, and no line can be drawn between stamen 

 and staminodium and between staminodium and petal — in genera of 

 the Nymphaeaceae, Calycanthaceae, Magnoliaceae. Some staminodia 

 are secretory organs, stamens or petals that have become primarily nec- 

 taries — Coptis. Vestigial stamens, stamens in process of reduction and 

 disappearance, are commonly called staminodia. The remnants of sta- 

 mens, often mere stubs, in pistillate flowers are good examples of this 

 type. 



Staminodia, typically, have the vascular structure of stamens in more 

 or less reduced form. Where the stamen has lateral traces, these may be 

 weak or absent. Staminodia that are mere remnants of reduced sta- 

 mens may have no vascular supply or a mere basal stub. Vascular stubs 

 of the traces of stamens entirely lost externally may be present in the 

 floral receptacle, as in the flowers of the Scrophulariaceae and in the 

 pistillate flowers of some unisexual genera. 



