140 
R. Ruggles Gates. 
CHAPTER V. 
Parallel Mutations. 
For many years CE. lamarckiana was the only CEnothera known 
to exhibit mutations. Then mutations were discovered in a 
race of CE. biennis, one of which showed all the peculiarities of 
lata, but had the small flowers and other specific features of biennis. 
From this form the conception of parallel mutations and the 
recognition of their significance originated (see Gates, 1912a). 
Shortly afterwards Stomps (1912a) described independently the 
mutants nanella and semigigas from hybrids between CE. biennis 
and CE. biennis leptomeres Bartl. (—CE. biennis cruciata de V.) but 
apparently without recognizing the significance of their parallelism 
to forms derived from lamarckiana. CE. biennis mut. lata was 
later 1 described in detail and shown to have 15 chromosomes. It 
was clear that the same kind of germinal change was involved in 
both species. Two other probable mutations in CE. biennis, one 
a red-nerved form parallel to rubrinervis Gates, the other 
resembling Icevifolia, were also obtained. On these results the 
conception of parallel mutations was founded, and it has since 
been generally adopted by mutationists (see Stomps 1914, deVries 
1915b). 
Equally striking mutations have now been obtained from 
several species of CEnothera, including such wild species as (E. 
grandiflora, CE. stenomeres and CE. pratincola. In the last two 
species, some of the mutations are parallel to those described in 
CE. lamarckiana or CE. biennis, others are entirely dissimilar. A 
number of cases of clearly parallel mutations are put together in 
Table II, but a great many cannot readily be arranged in a table, 
and these will be discussed separately. From the table it will 
appear that three species have produced lata mutations (with 15 
chromosomes), while five have produced mut. gigas (28 
chromosomes) or mut. semigigas (21), and the same five species have 
given rise to dwarfs. These mutations have also occurred in 
various crosses. Virescence has also appeared independently in 
three species of CEnothera. 
Let us now consider the history of some of these mutations, 
especially in CE. biennis Linn., CE. stenomeres Bartl. and CE . 
pratincola Bartl., all of which have small flowers, are self-pollinated 
and rarely undergo natural crossing. The writer (1912, 1914) 
1 Gates & Thomas 1914. 
