i908] SHULL—M END ELIAN INHERITANCE 107 



delian, but still leave a doubt on account of the obvious derangement 

 produced by ill-treatment. 



In the summer of 1907 the seeds were sovm at the proper time 

 (April 30) and the Mendelian character of the branching habit was 

 fully established by the following facts: (a) Reciprocal crosses 

 (06356 and 06357), fully controlled, between two strongly branch ,^d 

 specimens belonging to the second of the two DR families mentioned 

 in 1906 (namely, no. 05150) gave 65 fully branched individuals in 

 the one family, 13 in the other family, and no unbranched specimens 

 in either, thus showing that at least one of the chosen parents was an 

 extracted dominant (DD). The number of branches in both these 

 reciprocal families ranged from 10 to 25. (J) Properly controlled 

 pollinations we re made between two specimens of the last family (05 145) 

 mentioned for 1906, supposedly a recessive family. The pistil- 

 parent had two strong branches, one of which showed an abnormal 

 bifesion. The poUen-parent had one strong lateral branch which ex- 

 ceeded the main stem. The cross was made between two heads borne 

 by lateral branches. Of the 22 offspring produced (06353), 19 "^'ere 

 wholly unbranched, two had one smaR branch, each near the base of 

 the stem, and one had two smaU branches similarly located. This 

 demonstrated that both parents were pure recessives and showed that 

 the branches produced the preceding year had no hereditary signifi- 



cance. 



Another sowins: (o6^t;2) was mad 



the same pistil-parent as the last. The 91 offspring consisted ot 67 

 individuals having less than 7 branches each and 24 having more than 7 

 branches each, the latter group havmg an average of about 16 branches 

 and the former group an average of less than two branches {fig. j). 

 As the branched iy^ does not usuaUy have more than 4 or 5 vacant 

 axils above the highest branch, one individual having 8 branches 

 and 10 vacant axfls probably belongs with the unbranched class. 

 The result in this family shows that about one-fourth ot the pollen 

 received by the unguarded mother came from branched indinduals, 

 and as this fact was made obvious in the first generation it gives further 

 proof of the dominance of the brandling habit over the unbranched. 

 Furthermore, it iUustrates weU how impossible it would be^ to 

 discover Mendelian ratios in cross-fertilizing species or ^-a^etles with- 

 nnt r^r.fnl rnntrol of fertilization. This requireir.iit accounts for 



