CONSTANCE: SYSTEMATICS OF THE ANGIOSPERMS 423 



this entire group of proposals, Arber's pithy comment on Zimmermann's "Merk- 

 malsphylogenie" is equally pertinent. She characterized his approach as "rela- 

 tively confused and incoherent — an inevitable result of the attempt to fit the 

 facts of floral structure into a scheme based upon the organization of a group 

 with which it may well be that the forbears of the angiosperms never had any 

 connection" (1937, p. 178). 



Far more serious has been the challenge hurled by those who, on the basis 

 of physiological and ontogenetic processes, have called into question the basic 

 homology of flowers with vegetative shoots and of floral and foliar structures. 

 Thompson (1935, 1944), rebelling against the formalism of the classical con- 

 cept, argued that a flower is primarily a "sporogenous axis" bearing emer- 

 gences, and that it is in no way comparable with a leafy shoot; Belin-Milleron 

 (1951) echoes this view, and Philipson (1949) seems to give it some support. 

 Gregoire (1931, 1938) maintained that reproductive and vegetative apices, be- 

 cause of their organization and relationship to the plant body, the mode of de- 

 velopment of the procambium, and the origin of their appendages, are "irre- 

 ducible" entities. This position has been supplemented with evidence from phyl- 

 lotaxy by Plantefol (1947, 1949), who thought that only the sepals possessed 

 homology with foliage leaves. (Some of these ideas have been reviewed by Ban- 

 croft, 1935; Kozo-Poljanski, 1936; Arber, 1937; Foster, 1939; Troll, 1939a; Un- 

 ruh, 1939; Wilson and Just, 1939; Matthews, 1941; Watson; Ozenda, 1946, 1949; 

 Joshi, 1947; Philipson, 1949; Kasapligil, 1951; and Tepfer, 1953.) Working with 

 periclinal chimeras, Satina and Blakeslee (1941, 1943) have drawn the inference 

 that sepals and petals are truly foliar, but that stamens and carpels are not be- 

 cause of their initiation in less superficial cell layers. 



Those who have read a peltate organization into some foliage leaves and 

 most fioral organs, have found in this conception furtlier grounds for maintain- 

 ing the basic homology of these structures (Troll, 1927, 1932, 1934, 1939a, 1939b; 

 Schaeppi, 1936, 1939; Kaussmann, 1941; Leinfellner, 1950, 1951; Baum, 1950). 



By assuming that vascular tissues are slower to undergo cohesion, adnation, 

 or abortion than are the organs they supply, it becomes possible through ana- 

 tomical investigation to detect the phylogenetically earlier condition of a speci- 

 alized flower (C. V. Rao, 1951). This idea of conservatism of the vascular tissues 

 has been emphasized particularly by Saunders (1937-1939, 1939) and by Fames 

 (1926, 1931) and his students. Saunders, indeed, carried this principle so far 

 as to attribute virtual independence to every floral trace, especially of the gynoe- 

 cium, a position which Fames has attacked vigorously. Puri (1951, 1952a, 1952b, 

 1952c) describes an hypothetical standard flower as one which is pentacyclic 

 (two perianth whorls, two staminal, one earpellary), each whorl receiving dis- 

 tinct vascular bundles from the stele. Fach sepal would receive three, each petal 

 one, each stamen one, and each carpel three; in this skeletally primitive flower 

 there would be no cohesion or adnation of these bundles. Although Arber scolds 

 such usage of "floral anatomy ... as a reliquary to be rifled for 'ancestral 

 traits' " (1933, p. 240), and numerous authors have shown that the vascular 

 supply may be less, more, or equally persistent than the organ itself (Smith, 

 1926; Fggers, 1935), there seems little doubt that vestigial vasculation may some- 

 times afford phylogenetically valuable evidence. This approach has now been 

 applied to members of many orders with the objective of clarifying floral struc- 



