52 Inheritance in Pisum 



length of 1^ inches. In i^j. the preponderating type resembled the i^i 

 plants, and the appearance of dwarfs, shorter than either parent, with 

 internodes of 1"0 — 1'2 inches in length (the proportion of long to short 

 being 19 : 6), confirms our belief that the characters thick and thin 

 stem, long and short internodes were the chief stature-factors involved 

 in this cross. Probably the difference in the number of^niodes intro- 

 duces a complication, but the small numbers grown in F^ and the lack 

 of further records, prevent a full analysis. We should mention that 

 this cross was made primarily by Mr Lock with the object of inves- 

 tigating the characters of the testa of the seeds of Pisum. 



In conclusion, with respect to the question of tallness and dwarfness, 

 it is evident that a closer investigation will reveal facts of great import- 

 ance to an understanding of the physiology of growth. 



Time of flowering : earliness and lateness. Certain varieties of peas 

 are well known and prized for their stability with respect to time of 

 flowering, and therefore it is to be supposed that the character is 

 hereditary. Mendel many years ago commenced experiments with a 

 view to determine the mode of inheritance, but few records of these 

 experiments are left to us. In Mendel's memoir on the hybridizing of 

 peas (1909b) we find the following: — "As regards the flowering time 

 of the hybrids the experiments are not yet concluded. It can, however, 

 already be stated that the time stands almost exactly between those of 

 the seed and pollen parents, and that the constitution of the hybrids 

 with respect to this character probably follows the rule ascertained in 

 the case of the other characters." 



By the use of the varieties Autocrat and Bountiful for such an 

 experiment, the advantage is gained of a long space of time between 

 the flowering periods of the two varieties : the former variety flowers, 

 in normal seasons, about 30 days after the latter. Thus, in 1909, from 

 sowings made in April, 23 out of 28 plants of Bountiful were in flower 

 on June 2nd, whereas Autocrat, sown at the same time, was only 

 just coming into flower on June 30th (see Table I). In spite, how- 

 ever, of the favourable nature of our material with respect to the 

 character under consideration, we cannot claim to have arrived at a 

 complete understanding of the mode of inheritance of earliness or 

 lateness of flowering. Nevertheless, we publish our records, and our 

 attempts to analyse them in Mendelian terms, since they appear to 

 show definitely not only that the problem is capable of solution, but 

 also the nature of the difficulties which have to be met before the 

 solution is obtained. It will be seen from the records of the time of 



