A TETRACOTYLEDONOUS RACE OF PHASEOLUS 



VULGARIS 



J. Arthur Harris 



Station for Experimental Evolution 



I. Introductory remarks 



The practical utility of cotyledon number in schemes of classi- 

 fication has been the cause of great emphasis being tacitly laid 

 upon the constancy and fundamental significance of this character. 



The tenability of such a position has been considered by various 

 writers. In part this has been quite incidental to a discussion 

 of the homology of the cotyledon, as, for example, in the paper by 

 Lyon^ and in some of the older morphological literature to which 

 reference may be obtained from papers cited below. In larger 

 measure the discussion has centered directly on the problem of the 

 origin of the monocotyledons. Sargant in 1902'^ and again in 

 1903^ contributed extensive data from seedling stages to the prob- 

 lem. At about the same time my interest in the questions was 

 aroused by anomalous seedlings of Pachira of the Malvaceae^ and 

 in an early discussion" I outlined some of the chief problems 

 requiring investigation. More recently Coulter and Land^ and 

 Coulter^ have discussed the subject upon the basis of embryo- 

 logical evidence. 



These papers deal primarily with the problem of monocotyledony 



^ Lyon, M. E. The phylogeny of the cotyledon. Postelsia i : 57-86. 1902. 

 2 Sargant, E. The origin of the seed-leaf in monocotyledons. New Phytologist i : 

 107-I13. 1902. 



* Sargant, E. A theory of the origin of the monocotyledons founded on the structure 

 of their seedlings. Ann. Bot. 17: 1-92. pi. 1-8. 1903. 



^ Harris, J. Arthur. The germination of Pachira, with a note on the names of two 

 species. Trans. Acad. Sci. St. Louis 13: 203-209. pi. g~ii. 1903. 



^ Harris, J. Arthur. The importance of investigations of seedling stages. Science 

 n. 22: 184-186. 1905. 



* Coulter, J. M.,& Land, W. J. G. The origin of monocotyledony. Bot. Gaz. 57: 

 509-519. pi. 28-29. 1914- 



^ Coulter, J. M. The origin of monocotyledony. Ann. ]VIo. Bot. Gard. 2: 175-183. 

 1915. [lUust.] 



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