54 Inheritance in Pisum 



We suggest therefore that lateness is dominaut to earliness, and that 

 the reason why the plants of F^ flower before those of the late parent 

 Autocrat, is that they possess the factor for long internodes, their 

 gametic constitution being TtLl. The fact that the position of 

 the flowers on the stem, in F^ plants, is about the same as in 

 Autocrat, lends some support to the view that late is dominant to 

 early. There was however a considerable range of variation in this 

 character, both in Autocrat and in the F^ plants. Moreover, owing to 

 the branched habit of Autocrat and of the ^i plants, and to the fact 

 that this character was not considered until rather late in the season, 

 it was impossible in some cases to recognise the main stem, i.e. the 

 stem which flowered first, and this may have spoilt the records to 

 some extent. This character of the position of the first flowers on the 

 stem has been supposed to indicate time of flowering (1905b). Our 

 records show that Autocrat bears its first flowers, on the average, at the 

 thirteenth node. Bountiful at the seventh node, and the ^i plants at 

 the twelfth. Many records of this character were made among the F^ 

 plants. The average result of these records points to the conclusion 

 that low-flowering indicates earliness, high-flowering lateness, but there 

 were many exceptional cases among individuals. Further investiga- 

 tions among F^ families, homozygous in respect of the many other charac- 

 ters involved, should provide a solution to this question. 



Proceeding then on the basis that lateness is dominant to earliness, 

 we observe, in the F^ generation, that the flowering period spreads over 

 more than a month, from June 2nd — July 6th, that whereas many (36) 

 plants of F2 flower as early as the early parent, few flower so late as 

 Autocrat (Table I). That time of flowering is influenced by seasonal 

 conditions is undoubted ; but the marked differences in flowering-time 

 between the various plants of F^ show that the mode of influence of a 

 given season is determined to a surprising degree by internal factors. 

 A more detailed examination of the distribution of earliness and late- 

 ness of flowering among the F^ plants, brings out several facts which 

 lend support to the conclusions that time of flowering, though inherited, 

 is modified in its expression in the zygote by morphological characters 

 such as thickness of stem. As we have shown, the F^ plants group 

 themselves into four classes: — thick long {TL\ thick short {Tl), thin 

 long {tL), and thin short {tl). If we chose arbitrarily the date of 

 flowering of Bountiful (June 2) as early and regard for our immediate 

 purpose all plants flowering after this date as late, we find, on scruti- 

 nizing the distribution of lateness and earliness among these classes, 



