, 



MA4N 



DEPT 



Defective inheritance-ratios in Bursa hybrids. 



By Dr. George Harrison Shull' r 



Station for Experimental Evolution, Cold Spring Barber, J 



New York. 



(Sonderabdruck aus dem XLJX. Bande der Verhandlungeii des naturforscheoden Vereines in Brunn.) 



Several years ago (1905 1907) I was making extensive 

 [cultures of .Bwrsa (Capsella) bursa-pastoris, of Bursa Heegeri, and 

 of hybrids between these two species. Bursa Heegeri is generally 

 conceded to have originated from B. bursa-pastoris by a recent 

 mutation and has been found in nature only once in a situation 

 r hich would warrant the belief that it had not been derived 

 from a near - by experimental culture. Although a number of 

 [specimens were found by Professor H e e g e r at the original locality 

 [on the market-place at Landau, Germany, in 1897, so far as is 

 low known these represented a single elementary form or biotype . 

 Sfll bursa-pastoris, on the other hand, is of almost world- wide 

 distribution, and presents an unknown number, but certainly a 

 |large number, of distinct biotypes. 



In my cultures of the latter species I found four forms of 

 -osette which were related to one another as the four terms of 

 Mendelian di-hybrid. These four biotypes were named and 

 | described as follows: 1 ) 



Type (a). Bursa bursa-pastoris heieris has the leaves divided 

 to the mid-rib, the terminal lobe being usually separated from 

 [the nearest lateral lobes by clean, deep incisions. The lateral 

 lobes consist essentially of two features, an elongated proximal 

 [portion, the primary lobe", and a more or less rounded or 



J ) ^Results of crossing Bursa bursa-pastoris and Bursa Heegeri u . 

 pp. Proceedings Seventh International Zoological Congress, Boston Meeting, 

 LUgust 1924 1907. n Advanced reprint" issued in 1910. 



n Bursa bursa-pastoris and Bursa Heegeri: Biotypes and hybrids", 

 pp., 23 text^figg., 4 pis., Publ. No. 112, Carnegie Institution of 

 [Washington, 1909. 



Yerbandlungen des natarf. Vereines in Brunn. XUX. Band. * 



646272 



