82 
R. Ruggles Gates. 
The Swedish race of CE. lamarckiana also yielded not only 
lata and semilata but also another form, having 15 chromosomes, 
called incuvvata? One of the latter when selfed yielded 5 incurvata 
and one like lamaYckiana. In this case there is more probability 
that a different chromosome was involved as the extra one, since 
no latas appeared in the offspring of incuvvata. But there is no 
certainty owing to the small numbers involved, an unfortunate 
result of the great amount of sterility in all these forms. 
Other forms having 15 chromosomes will be considered in the 
discussion of parallel mutations, but it may here be pointed out 
that a race of CE. biennis produces a lata mutation which is an exact 
parallel to the lata from lamarckiana , and which has 15 
chromosomes 2 . In the biennis from the Holland sand dunes, known 
to have been naturalized there since the time of Linnaeus, Stomps 
(1914) obtained a semigigas mutant. When pollinated by de Vries 
(1915b) with pollen from pure (E. biennis without the flowers being 
castrated, it produced 19 offspring,—one dwarf, 10 biennis with 
14 chromosomes and 8 of a new unnamed type having 15 chromo¬ 
somes. The latter shows no resemblance to lata, but from the 
description it appears to have several characters in common with 
incuvvata. It strongly supports the evidence from incurvata that 
independent 15-chromosome types exist. Regarding its origin in 8 
individuals from a cross, one must suppose that the reduction 
divisions in the megaspores of CE. biennis semigigas produced 
embryo-sacs, about half of which contained eight chromosomes in 
their nuclei and half seven chromosomes, the remainder having 
been extruded or lost through irregularities in division. That such 
extrusion was not a haphazard and irregular phenomenon, however, 
isindicatedby thefactthat these 8 individuals all belonged to one type. 
Another lata-Mke mutant was obtained by de Vries (1915b, 
p. 186) from CE. lamavckiana x CE. biennis nanella. It had in 
addition to the marks of lata the characters of the ordinary hybrid 
type CE. lamavckiana x biennis , and confirms the conclusions of the 
writer 8 regarding the origin of CE. lata vuhricalyx and other lata- like 
forms in hybrids. 
Finally we may consider the important studies of Miss Lutz 
(1916, 1917) on forms with an extra chromosome. It is to be hoped 
that her counts of chromosomes, which appear hitherto to have 
been made almost entirely from root-tips and other somatic tissues 
1 The Mutation Factor, p. 147. 
2 Gates and Thomas 1914. 
2 Gates, 1914, p. 265. 
