SQME NEW CASES OF MENDELIAN IXHERITA^XE 



George Harrison Shull 



(with four figures) 



In crosses between nearly related elementary forms, numerous 

 investigations have shown that a very wide range of characteristics 

 in a great many species of both plants and animals behave in the Mcn- 

 delian way; that is, they give a uniform progeny in the first hybrid 

 :encration (F,), and show perfect segregation of the various character- 



istics in F, and later generations. So consistent have been the results 

 that there can be no question that Mexdel's law has fundamental 

 and widespread applicabflity, but it has also been demonstrated that 

 it has its limitations. Where these limitations lie and why it is thus 

 limited may not be known until a much larger mass of data is on 



record than is now available. 



Several of the cultures at the Station for Experimental Evolution, 

 upon which no report has yet been published, present new mstances 

 of Mendelian heredity under conditions which make their considera- 

 tion desirable, even though only a preliminarj- account can be given 



at this time 



HELLiNTHUS AN^NXUS L. 



Among 112 plants of the so-called "Russian" sunflower (Heli- 

 anthus anntius var.) grown at the Station during the summer of 1904, 

 aU but one had the usually unbranched stem surmounted by a smgle 

 large head. Sometimes these had several weak branches in uie axils 

 of several of the lower leaves, but there were never more than three 

 or four of these lateral branches, and none ever stood higher on ttie 

 stem than the fifth node above the cotyledons. The one exceptional 

 individual had strong branches in nearly all of the axils and bore a 

 number of somewhat smaEer heads, but was not obser.-ed to differ m 

 other respects from its unbranched neighbors {figs, r, 2). Ihe seeas 

 had been purchased at a seed store, and nothing is known ot the 

 antecedents of these plants. 



[Botanical Gazette, rel. 45 

 103] 



