354 



Tricot\loiis Races. 



half race occur in the intermediate race also, and as a 

 rule all of them in every sowing, provided it is not too 

 small. On the other hand, if the half race is cultivated 

 on a sufficiently large scale, it will contain all the forms 

 of the intermediate race. There is no morphological 

 limit between the two, although the physiological one is 

 perfectly definite, and in my experiments has never been 



15 ?0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 

 1 1 2 1 1 6 9 10 7 16 13 13 15 3 1 0. 



Fig. 67. Oenothera hirtella. Tricotyloiis 

 intermediate race ; curve of hereditary 

 capacities of plants of 1896, including 

 both atavists and tricotyls. The ca- 

 pacities oscillate between 15 and 95%. 

 The meaning ef the figures is the same 

 as in Fig. 66. 



0.1 0.4 0.7 1.0 1.3 1.6 1.9 2.2 2.6 2.8 3.1 3.6 3.7 

 26 16 14 10 9 3 6 8 11. 



Fig. 66. Oenothera ruhr'i- 

 nervis. Tricotylous half 

 race. Curve of the he- 

 reditary capacities of 

 the plants of 1894. The 

 highest of these was 

 Z-7%- The upper row 

 of figures relates to the 

 percentage composition 

 in tricotyls, the lower 

 to the numbers of 

 seed-parents with this 

 composition. The ordi- 

 nates have the same 

 signification as these 

 latter figures.^ 



overstepped. The tricotyls of the half race do not lead 

 on to the intermediate race, nor do the atavists of this 

 race lead on to the half race. The two races are just 



^ The percentage figures are calculated, in this experiment, from 

 counts made on 300 seedlings from each plant ; but the number of 

 ordinates is reduced to one-third. Therefore o.i means, o — 0.2; 0.4, 

 0.3 — 0.5 and so on. The tricotylous race-s of Dracocephaluin uwlda- 

 ricum and Penstemon gentionoi'des gave similar curves. (Harvest 

 of 1894). 



