MUTATION IN MATTHIOLA 241 



The plants were grown in house C of the previous work. Two or 

 three plants (one shown in fig. 25) were extremely vigorous, pre- 

 sumably because of some accidental soil difference; aside from these, 

 a few apparent mutants, and a few plants otherwise abnormal, the 

 plants were fairly uniform except where heterozygosis was to be 

 expected. 



The data for time of flowering, as with the 1908 cultures, show the 

 same main features as the internode data, and only the latter will be 

 considered in detail. The types were again more widely different in 

 internodes than in earliness, a fact which seems to indicate that the 

 early type grows more slowly than Snowflake. 



So large and so regular are the differences in internodes that the 

 means of these very small lots seem worthy of presentation (chart I). 11 

 Apparently the few-noded character was carried, among the nine 

 parents descended from WG9-C10, by all except the three parents 

 having the highest numbers in their respective houses. 



Tables 8 and 9 give the internode frequencies for the singles and 

 doubles respectively, by separate progeny lots and by groups of similar 

 ancestry. The range of variation for the check lots, omitting the 

 indicated apparent mutants and other apparently abnormal plants, is 

 rather surprisingly small, as is the case with the cool-house cultures 

 of 1908. The three late progeny of WG9-C10 give lots closely corre- 

 sponding in range to the check lots, only one individual falling below 

 the range of the combined check lots. The six early and medium 

 progeny of WG9-C10, on the other hand, give distributions of far 

 greater range than do the check parents, extending to much lower 

 values. 



Tables 10 and 11 give the ordinary statistical constants for the 

 grouped lots. The mean number of internodes, for both singles and 

 doubles, is about 25 per cent lower in the progeny of the six few- 

 noded parents, the difference being not far from ten times as great as 

 its probable error. The increase in variability with the progeny of 

 the early parents is also striking, and the difference is about five to six 

 times its probable error. With time to flowering, it may be noted, the 

 differences are similar to those with internodes, but somewhat less 

 marked in the case of the mean ; the flowering data are not given here. 



It is plain that the previous conclusion as to the heterozygous nature 

 of WG9-C10 is sustained. The elimination of the apparent mutants 



n Calculated with the apparent mutants and four other apparently abnormal 

 plants eliminated; see tables 8 and 9. 



T991 



