RESULTS OF CROSSING BURSA BURSA-PASTORIS AND 

 BURS A HEEGERI 



GEORGE HARRISON SHULL 



TEN years ago Solms-Laubach received from Heeger some 

 specimens of a Cruciferous plant which was found growing in 

 nature at Lindau, Germany, which the latter could not identify. 

 In general habit these plants resembled the almost cosmopolitan 

 species, Bursa bursa-pastoris (L) Britton or Capsella bursa-pastoris 

 as it is commonly called by European botanists. They differed from 

 the latter species, however, in having seed capsules oval in outline 

 and circular in cross-section instead of the flat and triangular or 

 obcordate capsules which are characteristic of Bursa bursa-pastoris. 



Solms-Laubach and Ascherson to whom he showed the specimens, 

 were both inclined at first to refer them to the genus Camelina, which 

 is characterized by spherical capsules. Cultures made from seed se- 

 cured from Professor Heeger soon indicated, however, the near rela- 

 tionship of the new form to Bursa bursa-pastoris when in 1898 several 

 apparent reversions to the capsule-form of B. bursa-pastoris were 

 noted. In 1900 Solms-Laubach * published an account of the new 

 form, assigning to it the name Capsella heegeri which becomes, ac- 

 cording to the American code, Bursa heegeri (Solms-Laubach). 



This very distinct species of Bursa has attracted considerable 

 attention for the reason that its occurrence as a component of the 

 flora of a region so well known taxonomically could leave scarcely a 

 doubt of its very recent origin from B. bursa-pastoris by mutation, 

 and it was mentioned by De Vries 2 as an instance of mutation in 

 nature. Shortly after the publication of the original account, Bursa 

 heegeri disappeared from the type locality at Lindau, and has been 

 reported from nature only once since that time, though it has been 

 widely grown in botanical gardens. 



The second report of the discovery of Bursa heegeri in nature was 

 made by Laubert 3 who discovered it along the Dahlem turnpike in 

 1905, but here the likelihood of a new origin is certainly exceeded by 

 the likelihood that a seed was carried to this spot by some agency 

 from a nearby culture, for it had been cultivated for several years at 

 Dahlem in an unprotected bed several hundred meters from the 

 place in which Laubert discovered it. Laubert pointed out that there 



1 Solms-Laubach, H., Cruciferienstudien I. Capsella Heegeri Solms eine 

 neuentstandene Form der deutschen Flora. Bot. Zeit., 58, pp. 167-190, PI. VII. 

 1900. 



2 De Vries, H., Die Mutationstheorie. I. Die Entstehung der Arten durch 

 Mutation, pp. 477-478. 1901. 



3 Laubert, R., Notizen iiber Capsella Heegeri Solms. Verh. des Bot. Vereins 

 d. Provinz Brandenburg. 47, pp. 197-199, 1905. 



