6o 
ANNE M. LUTZ 
apparently always degenerate. Similarly, when such an irregularity 
occurs in the megaspore meiosis, if the 8-chromosome megaspore 
functions it will, after fertilisation by a 7-chromosome pollen grain, 
give rise to a lata-Uke mutant. . . . Moreover, in lata or semilata 
when crossed with their 14-chromosome parents or when self -pollinated, 
the percentage in which the mutant reappears will depend upon the 
relative number of their 8-chromosome and 7-chromosome germ- 
cells which function." 
The authors then state that the frequency of this unequal division 
appears, from the observations of Gates to be ''of the order of i per 
cent." This, they say, would give about two 8-chromosome pollen 
grains in 400, or 0.5 percent, and that "If the frequency of this ir- 
regularity in the megaspore mother-cells is the same, about i per cent, 
of lata mutations should be anticipated." 
Gates's claim that "whenever a meiotic irregularity leads to the 
formation of an individual having an extra chromosome, such a plant 
will have the leaves and habit of 0. lata or 0. semilata " leaves no 
loophole for escape from the conclusion that all 15-chromosome off- 
spring of 14-chromosome forms — or at least all which are derived from 
the fertilization of an 8-chromosome egg by a 7-chromosome sperm 
— "have the leaves and habit of 0. lata or 0. semilata,'' while Gates 
and Miss Thomas's estimates of the percentages of offspring of 0. lata, 
selfed, and of 0. lata X 0. Lamarckiana which may be expected to 
reproduce the characters of 0. lata, lead the reader to conclude that 
progeny resulting from 8+7 unions invariably have the characters 
of 0. lata, 0. semilata, or some lata-like form. 
All of the 15-chromosome mutants which Gates and Miss Thomas 
mentioned in this report and which Gates has discussed in earlier 
publications, were classified as 0. lata,^^ 0. semilata, lata to semilata 
or lata-like forms, and it appears that these were the only 15-chro- 
mosome mutants whose somatic chromosome numbers had been 
ascertained by them at that time;^^ if such be the case, this chance 
occurrence is probably responsible for their conclusions. That many 
of the 15-chromosome mutant offspring produced by 14-chromosome 
forms have lata or lata-like characters cannot be questioned, but it is 
equally certain that a far greater number do not. It seems to the 
1° Including 0. lata rubricalyx and 0. biennis lata. 
As we have seen, Gates ('15a) has since reported a 15-chromosome mutant, 
0. incurvata, which still later ('15&) he says is quite different from O. lata. 
