No. 646] SHORTER ARTICLES AND DISCUSSION 



463 



the small late plants approximated the familiar 9-3-3-1 group- 

 ing. If the assumption is made that all these late plants were 

 adherent, the percentage of adherent plants in most of the prog- 

 enies would then approximate the expected. For the present 

 analysis of the relationship of brachytic and adherent, the low 

 percentage of adherent plants is not important, since the per- 

 centage of crossovers can be determined from the ratio of 

 normal to brachytic plants or by the use of Yule's Coefficient 

 of Association.^ 



Combining the five progenies the distribution of plants is as 

 follows : 



Nor. ! AH. i T?a. Ttr 1 \A -P« ' AH -Tlr Pn .Rr Ad.-Ra. Small 



It is seen that the progenies of this hybrid indicate about 17 

 per cent, of crossing over while the three self-pollinated prog- 

 enies of the other hybrid, involving brachytic and adherent, 

 indicate 22 per cent, and the back crosses 30 per cent. It 

 seems inadvisable to combine the self-pollinated progenies from 

 the two hybrids to arrive at a single figure for the percentage 

 of crossovers since the degree of crossing over between two fac- 

 tors often varies greatly in different progenies. It seems certain 

 from these two hybrids that these two cliaracters are located 

 in the same chromosome separated by a distance varying from 

 18 to 30 units, thus making a linkage series of bracliytic, adher- 

 ent and pericarp color, 



3 Yule, G. Udney, "On the Association of Attributes in Statistics." PhU. 

 Trans. Boy. Soc, London, S. A., Vol. 94, pp. 257-319, 1900. 



