The Isolation of Tricotyloiis Intciinediatc Races. 427 



lire. Such a task I have, therefore, only undertaken 

 with a single species, Antirrhinum inajiis. 



Only some varieties of hemp seem to include tricotyl- 

 ous intermediate races. Amongst those which I have 

 tested I have found such a one in the giant hemp only. 

 In the spring of 1893 I sowed a large quantity of seed of 

 this species, but was only able to bring 7 tricotylous plants 

 to maturity. Unfortunately the majority of them were 

 male, and there was but a single female plant. This, how- 

 ever, produced four tricotyls amongst 126 seedlings. In 

 1894 two of these were female and two male. The seeds 

 of the former were saved separately and yielded 15 and 

 9% tricotyls amongst 400 and 600 seedlings respectively. 



For the continuation of the race, onlv the tricotvlous 

 seedlings of the parent with 15% were planted out 

 (1895). There were 29 plants, of which 10 bore seed. 

 Their values were 19—31—38—40—43—47—48—50— 

 52 and 63%. As we see they attained the mean value of 

 the intermediate race and even exceeded it in one case, 

 (63% amongst 316 seedlings). The tricotylous ofifspring 

 of this individual alone were planted out (1896). Of 

 these, 38 specimens set seed, and from this the values of 

 the individual parents were calculated. I reduced them, 

 as usual to groups with 40 — 45 and 50% etc.. as a mean 

 value, and found the 38 offspring of the parent with 63% 

 to be distributed as folows : 



Proportion of tricotyls 40 AS 50 55 60 65 70 75 80 

 Number of seed -parents 5 5 3105 5 2 2 1 



The mean of the series is at about 55%, and the 

 series therefore constitutes a good instance of a young, 

 isolated race whicli, however, has not yet been improved 

 to anv considerable extent bv selection. 



