MUTATION IN MATTHIOLA 231 



here the mutant types, with one exception, often failed to grow satis- 

 factorily or to set seed. Infection, probably by Fusarium, evidently 

 was the cause of the death of many of these plants in their second 

 season. 



With all cultures grown after (probably) those of 1906, special 

 care was taken to secure random samples of seed, and after 1908 no 

 plants were rejected. The only exception to this statement is the 

 rejection of one pot out of every fifteen, by number and systematically, 

 in the first twenty progeny lots of 1910. For the earlier cultures, a 

 certain amount of selection must be recorded, as follows. In 1906 

 the small and the largest plants were omitted at potting, and probably 

 any weak and abnormal seedlings had been omitted at the preceding 

 transplanting. In 1907 all markedly weak, late, or abnormal seedlings, 

 as determined mainly by the appearance of the cotyledons, were 

 omitted at the first transplanting; and the same was done in 1908, 

 except that certain lots from old seed were unselected. 7 



These last lots were arranged at transplanting in such a way that 

 the weak and abnormal plants came at the end in each lot. 



EXPERIMENTAL DATA 



THE OCCURRENCE OF APPARENT MUTANTS 



In the cultures of 1906, 88 plants were grown to maturity, none 

 of these being suspected of mutation. In the cultures of 1907, among 

 170 plants one striking variant appeared; this plant, WG9-C10, was 

 exceptionally small and early in blooming. 



In the cultures of 1908, 714 plants were available, including ap- 

 parent mutants in several hereditary lines as indicated in table 1. A 

 striking feature of the results is the scarcity of apparent mutants 

 among the seedlings classed as strictly normal at transplanting; prob- 

 ably the scarcity in the preceding years was due mainly to the rejection 

 of abnormal seedlings (see "Methods"). The first, second, and fourth 

 of these forms have been common in later cultures, while the third 

 and fifth have been rarer; the last three, if seen at all elsewhere, have 

 not being recognized as belonging to the same types as these three 

 plants. 



7 One tiny plant from WG9, probably not viable, was discarded. 



T89J 



