A. St Clair Caporn 265 



The 183 F2 ears, each representing a separate plant, were all rubbed 

 out and planted ; but although all had been measured for the purpose 

 of compiling Table II, they were not specifically identified in the 

 sowings. They yielded 170 ^3 rows with a sufficient number of plants 

 per row to permit of accurate classification. The segregation — an un- 

 doubted 1:2:1 ratio — is shown in Table II a. 



A series of sowings in which the glumes of the parents had been 

 carefully measured proved that the maximum for pure shorts was 

 12*5 mms. and the minimum for pure longs 18 mms., while the upper 

 and lower extremes of heterozygosity were 20o and 12 mms. respec- 

 tively. The extracted pure long types, it was fi-equently noticed, 

 seemed to be somewhat more compact than T. polonicum, and a more 

 careful study of them was therefore made. The glumes of the progeny 

 of certain pure longs of known size were measured and compared with 

 those of an equal number of Polonicum plants grown in the same 

 season and under identical conditions. 82 plants of each kind were 

 examined. The influence of the parental glume length on the progeny 

 in the case of these pure long forms was nil ; for a plant with a 19 mm. 

 value gave a row of offspring with the same average length as did one 

 of 275 mms. 



In Chart III the taller curve has been plotted from the extracted 

 pure longs (Table III), while the dotted curve represents the frequency 

 distribution of an equal number of Polonicum ears. The average 

 length of the former was 24-15 mms. ; that of the latter 29"23 mms. 

 The difference is very considerable. Furthermore, there is a tendency 

 towards greater uniformity among the extracted longs (cf the large 

 proportion of glumes 24 and 25 mms. long). In all probability the 

 extracted pure shorts exhibit much the same sort of alteration in 

 average value of the glume length when compared with the Eloboni 

 parent, with the difference that instead of being lowered, the average 

 length is increased. For although no proper comparison could be made, 

 owing to the destruction of the Eloboni stock, nevertheless, as far as 

 could be judged by instinctive eye tests, most of the extracted Elobonis 

 appeared to be appreciably longer in the glume. 



