A BIMODAL VARIATION POLYGON IN SYN- 

 DESMON THALICTROIDES AND ITS 

 MORPHOLOGIL SIGNIFICANCE 



DR. J. ARTHUR HARRIS 

 Carnegie Institution of Washington 



In the spring of 190b I had occasion to count the num- 

 ber of leaf lamina 1 in the involucres of a series of four 

 hundred inflorescences of Sifnriesmoii thalictroides col- 

 lected from the north slope of a hill at Meramec High- 

 lands, Missouri. In making the records, each distinct 

 lamina was counted, whether it was leaf or leaflet, the 

 immediate purpose of the work being to get some idea of 

 the variability in the number of divisions of the leaf sur- 

 face in the involucral whorl and the degree of interde- 

 pendence of the number of lamina* and the number of 

 flowers for comparison with studies already made of the 

 correlation between length of stalk and number of flowers 

 per umbel in Nothoscord'nim and Allium, 1 and between 

 number of flowers per inflorescence and number of ovules 

 or seeds per ovary in Cercis 2 and Celastms. 8 When I 

 gathered the material I was quite aware that this rough 

 method of lumping the lamina 4 is not sui-ted to bring out 

 the morphological significance of the data, but only a 

 little time was available for the work and for the purpose 

 then in hand the method of treatment seemed quite ade- 

 quate. 



These data are shown in the form of a correlation sur- 

 face in Table I. 



It is quite unnecessary to publish graphs for these two 

 distributions to show the conspicuously bimodal char- 

 acter. For the number of laminae, there are conspicuous 



a Harris^ J. Arthur, Ann. Eept. Mo. Bot. Card., Vol. XX, 1909. 



