I9I9I 



de vries—oexo thera r ubriner vis 



which possess the other characters of ruhrinervis, but lack the 

 brittleness, are easily recognizable as rosettes of radical leaves as 

 well as during the growth of the stems. They will be designated 

 as subrobusta .^ 



The determination of the percentage of mutants in self-fertilized 

 seeds was made in 19 16 in the following manner. The specimens 

 were counted in the boxes at the time of planting out in April and 

 the most undoubtful specimens of rubrinervis were counted and 

 destroyed. All the others were planted out and tried at the time 

 of flowering in August. By this means the space required for the 

 cultures was reduced to about one-half of what would have been 

 necessary if all the plants had been set out. Some losses were 

 unavoidable and the percentage figures may be a little too small 

 in ordinary cases. Only under favorable conditions do they come 

 up to the amount of the theoretical expectation, namely, one-third 

 of all the indi\'iduals. Since my question, however, was mainly to 

 decide whether all specimens of rubrinervis split into this form and 

 deserens, or whether there are also plants with a uniform progeny, 

 I shall give the figures as I found them. 



Percentage of O. deserens among cultltres of O. rubrinervis 



In the first place, I shall now describe the main line of 0. rubri- 

 nervis. Part of the seeds of the original mutant of 1895 had been 

 preserved until 1905; they germinated sufficiently and gave the 

 second generation. From this a third generation was derived in 

 1910, 1913, and 1914, and a fourth in 1913, 1914, and 1915. All 

 the parents of these generations have been artificially fertilized by 



s Gruppenweise Artbildung, p. 143. 1913. 



