184 Segreffation of a Quantitative Character in Beans 



in the first place any mathematical or statistical end in view, but are 

 only a summary expression of exact measurements, and become the 

 equivalents of such descriptive terms as red and white or smooth and 

 rough. 



The constancy of quantitative characters having been shown, it 

 remained to prove whether or not they behave in a cross like qualitative 

 characters, showing the usual forms of Mendelian segregation. Crosses 

 made between beans of different lengths and breadths showed segregation 

 similar to that where several cumulative characters are in question, as 

 Professor Johannsen points out in his Elemente der exakten Erhlich- 

 keitslehre, 2nd Ed. p. 558. And further he communicates interesting 

 results in connection with the origin of the mutation dealt with in this 

 paper and of another mutation. He finds that the latter mutation, 

 occurring as a heterozygote, gives the original form and a new form as 

 segregates in the simplest Mendelian ratio, 1:2:1. [Elemente, 2nd Ed. 

 p. 653.] 



The data to be dealt with in this paper are the results of a cross 

 between the pure line E and a long mutant from it, made in hope of 

 throwing some light on the nature of the mutation. I am indebted to 

 Professor Johannsen for the following account of the origin of the material 

 in question. 



" The beans used were a variety of Fhaseolus vulgaris nana called 

 brown Princess beans, cultivated for commercial purposes in certain 

 districts in Fyn. In 1901 a number of pure lines were isolated from 

 bought material. Only biotypes were chosen of which the seeds did not 

 touch each other in the pod, but developed quite freely. And all types 

 where there was a tendency to abortion, that is, where the pods were 

 not filled with seeds, were excluded. All the biotypes were therefore 

 from the beginning, healthy, fertile and with well-formed seeds, suited 

 to be measured singly with the apparatus described in the Elemente der 

 exakten Erhlichkeitslehre, 2nd Ed. p. ] 3. 



"As to fertilisation, many years' work with the pure lines in question 

 has shown that, when the beans are cultivated under a voliere of wire 

 netting with a mesh of about 2 cms. there is little chance of crossing. 

 And all the experiments made on these pure lines have clearly shown 

 their genotypical constancy ; all selection has been without result. Fur- 

 ther, in the crosses that have been made — and made only with great 

 difficulty — it has appeared at once that the conditions, as regards in- 

 heritance and variation, are quite different from the behaviour of pure 

 lines, as is pointed out in the Report of the Third International Con- 



