BATESON AND PUNNETT 



were raised in F.^ and F4, as is recorded 

 in Table II. The striking feature about 

 this series of experiments is that among 

 the coloured flowers hoods are only 

 found on the purples. Among some 

 thousands of plants, not a single 

 hooded red has appeared. Neverthe- 

 less, the existence of hooded red t>'pes 

 is well known in Sweet Peas. We are 

 therefore led to suppose that we are 

 dealing with a strain in which the fac- 

 tor for erect standard is alternative in 

 the gametes to the factor for blue: and, 

 conversely, that every gamete which 

 carries the factor for the erect standard 



57 



is devoid of the blue factor. Conse- 

 quently, for these two pairs of factors, 

 only two of the four conceivable 

 classes of gamete exist, viz., blue 

 hooded gametes, and non-blue erect 

 gametes. The spurious allelomorphism 

 (see p. 4), which we must assume to 

 exist between blue and hood on the 

 one hand, and between non-blue and 

 erectness on the other, does not allow 

 of the formation of purple erect, or 

 of red hooded gametes. If this assump- 

 tion is correct, there should follow 

 certain consequences which may be 

 tested by the data given in Table II. 



1. Every hooded purple must be homo- 

 zygous for the blue factor. 



2. Every red must be homozygous for the 

 erect standard. 



3. Every erect purple must be hetero- 

 zygous for both the erect standard and for 

 blueness, and must therefore give hooded 

 purples, erect purples, and reds, in the ratio 

 1:2:1. 



4. Every hooded white must be homo- 

 zygous for the blue factor. 



5. Since every hooded plant is homozygous 

 for purple, and since long pollen is partially 

 coupled with the blue factor, it follows that 

 round pollen should be much rarer among 

 the hooded than among the erect purples. 



In Experiments 48-53, six hooded purples, 

 although from families in which reds occur, 

 bred true to purple (except in so far as 

 whites might appear) . 



In Experiments 54-59, six reds were bred 

 from, and proved to be all homozygous for 

 the erect standard. 



The erect purples, whose offspring are 

 recorded in Experiments 1-47, all gave 

 hooded purples and erect reds. Of their 3707 

 coloured offspring, 902 were hooded purples, 

 939 were erect reds, and 1920 were erect 

 purples. 



In the only two cases in which the cross 

 between a hooded white and a red has suc- 

 ceeded, the coloured offspring have been 

 purple. We hope to obtain further results in 

 the present year. 



So far only two round hooded purples and 

 one round hooded white have been met with 

 in families heterozygous for hood and purple 

 (Experiments 1-47). With this point we shall 

 deal later, in connection with partial coupling 

 (see p. 13). 



The phenomenon of association of 

 hood with purple was also witnessed in 

 the F2 families resulting from the 

 Bush X Cupid cross, with which we 

 have already dealt in another connec- 

 tion (p. 2). Here, again, the hood oc- 

 curred in Fo, and only on the purples. 

 The numbers— 48 hooded purples, 89 

 erect purples, and 47 erect reds— are 

 very close to the expected ratio, 1 : 

 2 : 1. 



As stated above, in other strains red 



hooded forms exist. Experiments with 

 these types are in progress, but have 

 not yet been carried far enough to give 

 positive results. 



Partial Gametic CoiipVmg 



A. Betiveeji Pollen a?id Colour.— In 

 our last Report, we show ed that the 

 distribution of pollen characters, long 

 grains and round grains, was affected 

 by that of the colour characters, ac- 

 cording to a definite system, and we 



