No. 568] X CAPSELLA BURSA-PASTORIS ARACHNOIDEA 233 



character is dominant, though Mendel, in his experiments 

 with Pisum umbellatum, has shown it to be recessive. 

 No fasciation, thus far at least, has been noted in the 

 other forms used in these experiments. 



Summary 



A culture of Capsella Bursa-pastoris proved heterozy- 

 gotic, yielding certain new forms (X C. Bursa-pastoris 

 Setchelliana, XC. Bursa-pastoris Treleaseana, yG. Bursa- 

 pastoris arachnoidea and X C. Bursa-pastoris attenuata) , 

 as well as certain forms already described by Shull (C. 

 Bursa-pastoris rhomboidea and C. Bursa-pastoris sim- 

 plex) in the proportion 4:2:4:2:3:1. The distinction 

 between simplex and rhomboidea, both inter se and be- 

 tween them and the other forms, is readily made by any 

 one familiar with Shull's investigations. These two 

 plants agree in having the earlier leaves broad (Fig. 4). 

 The climax leaves of rhomboidea and simplex show 

 marked differences, especially, as far as the incision of 

 the blade is concerned. These incisions, in simplex, reach 

 a depth equal to approximately one fourth of the width 

 of the blade (Fig. 10). In rhomboidea the incisions are 

 deeper, reaching the midrib in the homozygous form 

 (Fig. 12). The leaves of the latter also show marked 

 secondary lobes. 



The distinction between X C. Bursa-pastoris Setchelli- 

 ana, x C Bursa-pastoris Treleaseana and X C. Bursa- 

 pastoris attenuata is made with greater difficulty. They 

 agree in having long and narrow first leaves. The climax 

 leaves of Treleaseana and Setchelliana Bhow marked 

 incisions, exceeding one fourth of the width of the blade, 

 and which may reach the midrib (Fig. 9). The latter 

 form also may show marked secondary lobes. 



Besides the phenotypes here mentioned occur two 

 others, the one, X C. Bursa-pastoris orbicularis, with an 

 almost orbicular first leaf (Fig. 13) and a climax leaf 

 greatly resembling that of simplex (Figs. 14, 15), though 

 differing in texture. This form has not been sufficiently 

 studied, but is believed to be identical with one known to 



