8o 
ANNE M. LUTZ 
1 5 -chromosome offspring, such an individual will have the leaves and 
habit of 0. lata or 0. semilaia invariably, or even in the majority of 
cases (Gates, '13) and (h) whether the frequency of the occurrence of 
an irregular distribution of the chromosomes of 14-chromosome plants 
into 6-8 groups may determine the frequency with which lata-Yike 
mutants will appear (Gates and Miss Thomas, '14). We have yet to 
consider (c) whether when 0. lata is crossed with its 14-chromosome 
parent, or is selfed, the percentage in which 0. lata appears among the 
offspring is indicative of the number of 9- and 7-chromosome germ- 
cells which function (Gates and Miss Thomas). This question will 
be treated under the following head. 
3. Are I ^-chromosome Forms Inconstant? 
Of the twenty-one 15-chromosome mutants which Gates and Miss 
Thomas reported, three were identified as 0. semilata, one as lata to 
semilata and two as semilata to lata. Referring to de Vries's cultures 
of 0. lata and 0. semilata they say (p. 527): "Oe. lata was classed by 
him as an inconstant species, but semilata was incorrectly classed as 
constant. They are both obviously inconstant, however, and the 
presence of the odd chromosome shows why this must be so.'' (Italics not 
employed in the original.) Gates ('15a, pp. 111-112) has since found 
that the mutant which he described as semilata is not the same as de 
Vries's mutant of this name, but has decided to retain the name for 
the form reported by Gates and Miss Thomas, since the Amsterdam 
type is extinct. Therefore, when it becomes necessary to distinguish 
between these two types, we shall designate them as 0. semilata de 
Vries and 0. semilata Gates, respectively. 
Gates and Miss Thomas's statement raises the question, Does the 
presence of the odd or extra chromosome necessarily render a form 
inconstant? Are 15-chromosome forms never constant? 
Since 15-chromosome forms produce, as a rule, no pollen, very 
little, or a moderate amount containing a high percentage of bad 
grains since seeds are obtained from selfed forms with difficulty, 
and when secured, usually a much lower percentage of these than of 
the seeds derived from 14-chromosome forms succeed in germinating 
in the short time commonly allowed them, their constancy has not 
been tested on an extensive scale. Inasmuch as we know that in 
22 Plants having more than 14, but fewer than 28, chromosomes are much more 
incHned to be male- than female-sterile. Just why this is so, is not yet clear. 
