I. Leitch 189 



Thus a new type, X, shorter and broader than the original E type 

 has been established ; the segregated M remains constant and the 

 apparent E seed gives plants bearing seed which is, plant by plant, 

 either X or £" or M. Taking these segregating rows alone, seven rows 

 in all, and counting on the charts what forms are M and what are 

 either E or A'^, the rows give respectively, 13 (E or A') and 9 (M): 

 17 (E or X) and 5 {M): 17 (E or Z) and 7 (M): 18 (E or Z) and 



2 (il/): 15 (E or Z) and 7 (M): 16 (E or Z) and 5 (M): and 10 

 (Eor X) and 3 (M); in all, 112 non-M and 38 il/, which is an ideal 



3 : 1 ratio. At first no significance was attached to this ratio. In view 

 of the intermediate between E and M, row 9 in 1915, and of the new 

 Z type, it was to be expected that il/ would also produce new extreme 

 types. 



To throw light on the questions which now arise the following 

 selection was made for further breeding ; two M types, the intermediate, 

 and four of the segregating types. The rows chosen were rows 12, 5, 14 

 and 21 (segregating), 9 (intermediate) and 18 and [20, 22] (M), and 

 these numbers have since been used to indicate the seven groups of 

 descendants. The following summary account of the further experi- 

 ments in each of the seven groups will be most easily understood if 

 reference is made while reading to the genealogical tables on pp. 202 — 4. 



As group 21 offers no complication of any kind it is a suitable 

 starting-point. For sowing in 1916 were selected four of the extremely 

 short types, two apparently E and two supposed M. The short were 

 planted in rows 53, 48, 41 and 7 in 1916 ; the E seed in rows 12 and 

 17 and the 31 seed in rows 34 and 22. From the distribution curves for 

 these rows it appears that the small types remain constant in position 

 relatively to the control curves from the original lines ; that the plants 

 from the M seed bear beans true to the il/ controls ; and, on the chart, 

 the two apparent E types give some plants with Z beans, some with E 

 and some with il/. With regard to the short A" type there might i)ossibly 

 be a question as to whether row 7 is identical with the three rows 53, 

 48 and 41. It might be supposed that 7 was an intermediate between 

 Z and E. To test the point three short variates and one long were 

 selected from 7 and planted in rows 63 (long) and 64, 65 and 66 (short), 

 in 1917. The curves for these four rows are practically identical and it 

 is certain that no segregation takes place. Further selection of plus and 

 minus variates in 1918 also failed to show any difference. That is to 

 say, to judge from group 21, the X type shorter and broader than E, 

 once isolated, is fixed and constant. 



