148 MORPHOLOGY OF THE ANGIOSPERMS 



it is unseparated if there is no clear limit of anther and filament. (Ap- 

 parently, no term is proposed for the stamen where the sacs project at 

 both ends of the connective.) Peltate stamens are epipeltate if filament 

 attachment is on the ventral side; hypopeltate, if on the dorsal side. 



In the second, more elaborate and morphologically more complex 

 interpretation of "peltate" form in the stamen, the stamen is considered 

 not merely shield-shaped but, like the carpel, a hollowed organ, ascidi- 

 form or utriculate. (For a general discussion of the peltate theory as 

 applied to sporophylls, see Chap. 5.) In the stamen, typical hollowed 

 forms do not exist, but examples have been incorrectly described as 

 evidence that they do. 



Evidence of peltate form in the stamen is seen, under this interpreta- 

 tion, (1) in ontogeny, where the early form is called peltate; (2) in 

 the so-called three-dimensional (as contrasted with so-called two-di- 

 mensional, dorsiventral ) form; (3) in organs transitional from stamen 

 to petal; and (4) in petals. Ontogenetic evidence is seen, under this 

 interpretation, in the early ontogeny where the anther is prominent and 

 may stand somewhat obliquely on a basal plate, which, much later, 

 becomes the filament. The oblique position suggests the form of a 

 simple, peltate leaf. (This obliqueness is, actually, merely the early ex- 

 pression of later extrorse or introrse dehiscence.) A slight median fur- 

 row, often present at the apex, is considered, under the peltate theory, 

 a vestige of the hollow of an ancestral utriculate stamen (Fig. 61a). If 

 the bulging anther base overhangs the filament primordium, as in arrow- 

 shaped anthers (Fig. 61e), the enclosed space is said to represent a 

 vestigial cavity. (These minor indentations are merely beginnings in the 

 elaboration of anther form, not vestiges of ancestral cavities; the distal 

 hollow is the beginning of the transverse furrow separating the anther 

 sacs; the lower hollow is formed by differences in diameter of anther and 

 filament, which are evident at an early stage.) The stamen is looked 

 upon, under the peltate theory, as a "three-dimensional" organ, because 

 of the thickness of the anther and the arrangement of the four sporangia 

 in four corners. But this structure is the result of the specialization of the 

 anther, the bringing of two of the four sporangia, originally in a single 

 plane, into a second plane. In some ranalian genera, there are distal 

 hollows in organs transitional between stamens and petals, as in the 

 petals of Coptis, Hellcborus, Aquilegia, Delphinium, Aconitum. These 

 hollows are secretory areas and definitely glands in petals or staminodes 

 (sterile stamens); they are not vestiges of the cavity of a tubular, an- 

 cestral stamen, as suggested under the peltate theory (see Chap. 6). 

 The best evidence that the stamen is not fundamentally a peltate, three- 

 dimensional organ is the type of primitive stamen clearly shown by the 

 Ranales — a simple, dorsiventral, laminar organ. 



