426 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



C. Gynoecium: The classical interpretation of the carpel, dating at least 

 from de Candolle, regards this organ as an infolded, leaflike structure with its 

 margins more or less fused and bearing ovules. Arber and Parkin made the 

 explicit statement: ''We regard the carpel as a megasporophyll, present in the 

 ancestor of the Angiosperms as an open leaf, bearing several ovules on its mar- 

 gins, and not unlike the megasporophyll of Cycas" (1907, p. 47). Chadefaud 

 (1936) would derive the angiosperm carpel directly from a cycadean sporo- 

 phyll, and Thomas at one time (1931) visualized the evolution of a Ranalian 

 follicle from a Seed Fern sporophyll by way of a Caytonialian fructification as 

 an intermediate stage. (Hirmer [1935] and Harris [1940, 1951a, 1951b] have 

 contended that Caytoniales are themselves Seed Ferns with clearly gymno- 

 spermous pollination, and hence that their structures are only analogous with 

 those of angiosperms.) The basic angiosperm carpel is usually regarded as hav- 

 ing been a few- or many-ovuled follicle with three vascular traces — one dorsal 

 and two lateral — although Fraser (1937) thought there might have been five 

 originally. Carpels were interpreted as peltate organs homologous with peltate 

 leaves by Troll (1932, 1934, 1939b), Eber, Schaeppi (1936), Leinfellner (1940, 

 1950, 1951), Sprotte (1940), and Baum (1948, 1949a, 1949b); only a few fami- 

 lies of Alismatales were credited with having epeltate ones. 



The fact that it is the last-formed and often an ostensibly terminal structure of 

 the floral axis, frequently with a complex vasculation, has caused the gynoecium 

 to be visualized also as a complex largely of cauline origin. It has been vari- 

 ously suggested: (1) that the carpels or the gynoecium are in all or in some 

 angiosperms "emergences" of an axillary or cauline nature without foliar ho- 

 mologies (Thompson, Gregoire, Satina and Blakeslee; Philipson, 1949; Plante- 

 fol) ; (2) that the gynoecium is a mixture of cauline and foliar elements, with 

 the cauline complement decreasing (Vuillemin, 1919; Neumayer) or increasing 

 (Ozenda) with evolutionary advance; (3) that the ovules were originally borne 

 naked on cauline placentae, the envelopment of which by a cupule or a whorl 

 of bracts has resulted in angiospermy (AVettstein, Thomas; Hagerup, 1938, 1942; 

 Langdon, 1939); and (4) that the carpels are formed from condensed dicho- 

 tomous branch-systems, either directly, or indirectly by way of "foliarized" 

 branch-systems homologous with foliage leaves (Zimmerman, Hunt, Emberger). 

 The division of gymnospermous sporangia into "phyllosporous" and "stachy- 

 sporous" by Sahni, has been extended to angiosperms with the assumption of at 

 least a diphyletic origin and the recognition of one line bearing ovules on sporo- 

 phylls (most angiosperms) and the other bearing them on cauline structures 

 ("Amentiferae," Caryophyllales, possibly Primulales) (Lam, 1948a, 1948b, 1950, 

 1952; Suessenguth and Merxmiiller). This suggestion is particularly noteworthy 

 when it is stated that the two conditions have been distinct since the Devonian, 

 and yet that the androecium may be "phyllosporous" and the gynoecium "stachy- 

 sporous" in the same flower! After undertaking a broad if superficial survey 

 of angiospermous material, van der Hammen concluded : "It provisionally seems 

 that the distribution of phyllospory and stachyspory in the Angiosperms is more 

 intricate than was originally conceived" (1948, p. 298). 



Considerably more promising is the discovery by Bailey and his co-workers 

 of the existence within woody Ranales of apparently primitive, stipitate, con- 

 duplicate, three-veined, styleless, unsealed carpels, bearing two independent ex- 



