CONSTANCE: SYSTEMATICS OF THE ANGIOSPERMS 451 



Thus, we are confronted by the paradox that, although similarities between 

 certain Ranales and certain monocotyledons are legion, they must have diverged 

 from a common ancestor before the development of vessels. My own suggestion 

 would be that a common origin for monocots and dicots is more likely than 

 wholly distinct origins, that the ancestral type might have been a woody, vessel- 

 less "Pro-Ranalian," and that the primitive monocot is perhaps best — but not 

 very well — represented today by certain Liliales which have retained a capacity 

 for relatively regular secondary growth. Some palms and Alismatales appear 

 to retain a less modified floral structure (apocarpy), but they seem precluded 

 by their other features from occupying a position anywhere in the huge evolu- 

 tionary gap which this suggestion envisages. It should not be forgotten that the 

 primitively vesselless dicots do not necessarily have floral structure apparently 

 as primitive as that of certain herbaceous Ranunculaceae. That some groups of 

 monocotyledons could have had a different origin from that here indicated does 

 not seem to be completely ruled out but, as in the case of the possible existence 

 of primitive herbs, the burden of proof is on the advocates of polyphylesis. 



BIBLIOGRAPHY 



Abbe, E. C. 



1935. Studies in the phylogeny of the Betulaceae. I. Floral and inflorescence anatomy 

 and morphology. Bot. Gaz., 97:1-67. 



1938. Studies in the phylogeny of the Betulaceae. II. Extremes in the range of varia- 



tion of floral and inflorescence morphology. Bot. Gaz., 99:431-469. 



Abbe, E. C., and T. T. Earle 



1940. Inflorescence, floral anatomy and morphology of Leitneria floridana. Bull. 

 Torrey Club, 67:173-193. 



Allen, C. E. 



1940. The genotypic basis of sex expression in angiosperms. Bot. Rev., 6:227-300. 



Ames, O. 



1937. Pollination of orchids through pseudocopulation. Bot. Mus. Leafl., 5:1-29. 

 1946. The evolution of the orchid flower. Amer. Orchid Soc. Bull., 14:355-360. 



Andreanszky, G. 



1950. Die Rechtlinien der Pflanzenphylogenie. Ann. Biol. Univ. Budapest, 1": 19-20. 



1952. Ueber die Rolle der limnischen Lebensweise in der Phylogenie der Pflanzen. 

 Acta Biol., 3:19-30. 



Ankermann, F. 



1927. Die Phylogenie der Monocotyledonen ; Versuch einer Einteilung der mono- 

 cotylen Pflanzenfamilien und ihre Stellung zueinander auf Grund der Mor- 

 phologic. Bot. Archiv, 19:1-78. 



Appl, J. 



1937. Versuch einer Ableitung der Monocotyledonen von den Lycopodiaceae. (Pri- 

 vately printed.) 



1937-1938. Die Filixabkommlinge der Angiospermen. Repert. Sp. Nov., 42:153-156; 

 43:77-80. 



1939. Der Ursprung der Karpelle. Biologe, 8:335-336. 



