No. 568] X CAPSELLA BURSA-P AST ORIS ARAC HNOIDEA 219 



The " narrows" in question, then, fulfilled our expecta- 

 tion on the basis of a zygotic constitution BBNn. In 

 some cases the percentages are too high, in others too low. 

 The total yields fairly satisfactory results, to wit: BBNN 

 22 per cent., BBNn 51 per cent, and BBnn 27 per cent. 

 Two tests of the extracted recessive, a homozygotic rhom- 

 boidea, were made. The cultures, No. 3,713, from a 

 guarded rhomboidea (30,412^1£2P3) and No. 4,113, from 

 an unguarded rhomboidea (30,412^i28P3), both derived 

 from plants of the supposed zygotic constitution BBNn, 

 yielded, respectively, 54 and 207 plants, all of which bore 

 the typical rhomboidea characters. 



In the cultures just tabulated, the plants of the sup- 

 posed zygotic constitution BBNn resembled the parent in 

 all respects. The form arachnoidea, in this case, must 

 have the zygotic formula BBNN. Unfortunately, in this 

 case also, it proved unfertile. 



A better acquaintance with plants of the zygotic consti- 

 tution BBNn led us to formulate certain differences be- 

 tween them and our original " narrow." Plants of the 

 BBNn character, readily can be segregated from those of 

 the BbNn character by somewhat narrower primary 

 lobes, split to the midrib and the development, in climax 

 leaves of well-grown specimens, of a secondary lobe, not 

 pronounced but recognizable (Figs. 8, 9). 



On the basis of these morphological differences, as well 

 as because of the behavior of the plant on breeding, I 

 propose to segregate it from type 4 under the name 

 X Capsella Bursa-pastoris Treleaseana. This form is 

 homozygotic for B, while Setchelliana is heterozygotic 

 for B. Both are heterozygotic for N. They may be ex- 

 pected to look alike during the early stages. Later they 

 show a difference, since the form containing Bb does not 

 develop sinuses as deep as the form containing BB. The 

 form Treleaseana, when young, can readily be distin- 

 guished from a heterozygotic rhomboidea (Bbnn) by the 

 relative width of the early leaves ; later such a distinction 

 is difficult (Figs. 4, 5, 7). If any distinction at all is to 

 be made, it should be made on the basis of the rounding 



