888 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 









Table 



Ci /*/)■)) / J 17,7/ /v7 





Spillman's Table No. 





Plat No. 



" Bald " 



'• Bearded " 









D2 



594 



40-6 









D8 



03-7 



201 









D9 



731 



27*1 



ail 



XIV . .H 







D10 



72-3 



277 









Dll 



71-4 



So t 









D15 



63-3 



36-6 









D16 



69-9 



29-1 



Total 







30 



2162*9 



795-2 



Average 









721 



26-5 



Actual ratio 



= 27 



1 



Mendelian ratio = 



3 : 1 



Iii the original cross, varieties with " bald heads " were crossed with 

 varieties with " bearded heads," the result being thirty hybrids with " bald 

 heads " and none with " bearded heads." In this case the " bald " character 

 is Dominant and the " bearded " Recessive. In the next generation the 

 thirty "bald " hybrids self -fertilised produced thirty plats of hybrids, each 

 containing two types, viz. Dominant and Recessive. Table C gives the 

 approximate percentages of each type found in each plat, and it will be 

 seen that, with a few exceptions, the figures fairly agree with the Mendelian 

 expectation of three Dominants to one Recessive, i.e. 75 % " bald " + 25 % 

 " bearded." 



The average percentage of the thirty plats works out approximately 

 72*1 Dominants to 26'5 Recessives, i.e. a ratio of 2*7 to 1, which is ap- 

 proximate to the Mendelian ratio of 3 : 1. 



That the average result in this case is not so close to Mendel as in 

 the two former tables is probably due to the smaller number of plats 

 involved. 



There are apparently no exceptions in regard to the Dominance of 

 "bald" in the original cross, though it is interesting to note that in 

 Table XII., where two " bald " varieties are crossed together, giving twenty- 

 seven " bald " hybrids, these hybrids self -fertilised produced a small per- 

 centage of "bearded " hybrids in five plats out of the twenty-seven, thus 

 suggesting that one of the varieties used in this cross was not pure and 

 constant. If this be so, it may possibly explain the few exceptions noted 

 under Tables A, B, and D, as these all apparently occur in that particular 

 cross (Table XII.) 



In the original cross, varieties of T. vulgare with "long heads " were 

 crossed with varieties of T. comjwctum with " short heads," the result 

 being ninety-seven "intermediate" or "semi-long," six " long," and five 

 " short." This result, it is important to notice, differs from Mendel's 

 experiment with Peas, inasmuch as the first generation is " intermediate " 

 between the parents, with no Dominance of either parent. But, as will be 

 seen in the above table, in the second generation the Mendelian Principles 

 work out admirably. 



In the second generation, ninety-five of the intermediate hybrids 

 self-fertilised produced ninety-five plats of hybrids, each containing three 



