No. 068] X CAPSELLA BURSA-PASTOR1S ARACHNOIDS A 217 



theheterozygote have the same appearance, the remaining 

 75 per cent, should resemble the parent (Fig. 9, b). 



But in one case (M,412), the parent being SA12BR9P9, 

 and open fertilized, the offspring- consisted of 26.3 per 

 cent, rhomboidea, 46.2 per cent, of the parental type and 

 27.5 per cent, arachitoidea. If our supposition as to the 

 zygotic constitution of the parent is correct, then the 

 zygotic constitution of the arachnoidea in this offspring 

 must be BBNN. In the case of a selfed attenuata, we 

 found that approximately 25 per cent, of the offspring 

 was composed of arachuoidea of the probable zygotic con- 

 stitution bbNN. Is it possible that any Capsella, homo- 

 zygotic for N, would have the appearance of arachmddca.' 

 This seems more than probable, and other evidence, to be 

 adduced later, appears to support this view. The historv 

 of the BBNnis as follows: 



During 1912 I grew No. 8,412 from seeds of a plant 

 which resembled the grandparent 4,108.6. It was com- 

 posed of 1,07!) individuals, among which various types, 

 such as "broad," "narrow" and "linear," could be rec- 

 ognized. Not all plants were thus classified, a fourth 

 group of "intermediates" being formed, indicating that 

 some of the plants, while in certain respects resembling 

 simplex and especially rhomboidea (deep lobing, second- 

 ary lobes), in other characters more closely approximated 

 the "narrows," since their early leaves had been noted 

 as "narrow." In the light of recent experience, it is easy 

 to see why the distinction was made, though at the time 

 the conception of the differences was most hazy. Several 

 of these "intermediates" were grown, and of these a 

 single one yielded the seed for the next generation. This 

 plant had been permitted to flower unguarded, but after a 

 number of capsules had developed on the main stalk, this 

 was decapitated and the sideshoots were allowed to de- 



