S. (\ IIahland lO:} 



thr tiiiii" Nvluii ihr K. «»r rn»sHi'.s I an<i 2 weir Imiii^ slinlitd a airrlnl 

 sonix'h l"aili'<l l(» r^Vful tin* pivsi'iu!*- nt .uiy insect likely tn (muihc cnms- 

 ftTtilisiilion. During th*- jM-riiMl whm tlw F. ai mtss 5 was in flower a 

 lari^' hbu'k rarjH'ntiT Ium- t X i/l(K'(tp(i sp.) mad*' ils apjieanince. an<l often 

 visiitMl tlu* Mowoix. liringhravy iMxIitMl this insect cansecl the extrusion 

 of the stigniJis of all the flowers which it visited, and it seems clear that 

 it is ea|K»ble of cross-pollinat inij th*- jjlaiits. The presence of a few 

 Darks in faniilii's which should have hied tiiie to l*ale, nnist. he .uscrilied 

 Ui ius activities. 



Genetii' HeUtiionaln p of Darh ((ml rule. 



( )n tht' evidt'uce so far jncsented il is |)enMissd)le to conchide that 

 the two typos of cowpea Hower, Dark and Pale, const it,ute an allelo- 

 inorphic jKiir. 



In order to state definitely that the two tyjies differ by a single 

 fivctor it must be shown that : 



1. A ratio of .S dominants to 1 recessive exists in F.,. 



2. The ratio of i)ure to heterozygous dominants is 1:2. 



3. The recessives all breed true. 



The results c<jnform to these conditions, for the ratio of pure to 

 heterozygous dominants as shown by their behaviour in F:i cultures is 

 88:35, i.e. 2*4 : 1*0, a fairly close approximation to expectation. Some 

 of the families were carried to ^4 and Fr,. The results are of no par- 

 ticular significance, as they merely serve to confirm those obtained in 

 previous examinations. 



(2) Dark by White. 



The F^ of crosses between Dark and White flowered types was Dark. 

 The results of the F.^ and F,, are presented in Tables V and VI. A 

 summary of the results is as follows : 



In F. the parental types reappeared and the ratio of Dark to White 

 w;vs 3 Dark to 1 White. In F,, three families only were grown. Two 

 of these were from F., Darks, and showed segregation into Dark and 

 White in the 3 — 1 ratio. The remaining family was from a White 

 flowered F., plant. It bred true to White. 



While the evidence does not permit of complete certainty attaching 

 tt) the conclusion that Dark and White also form an allelomorphic pair, 

 there can be little doubt that such an interpretation of the results is 

 justifiable. 



