549 
Gates .— The Trisomic Mutations of Oenothera. 
AIillation. 
Parent form. 
Author. 
Remarks. 
sublinearis, de Vries ? 
Oe. Lamarckiana 
de Vries, 1909 
This is based only on 
genetic behaviour. 
elliptica, de Vries ? 
nanella lata 
dwarf type 2256 
Oe. nanella 
11 
Lutz, 1917 
)) 
aberrans , Lutz 
Oe. lata x Lamarckiana 
Lutz, 1916 
I 4 +1 chromosomes. 
rubrinervis , de Vries 
Oe. Lamarckiana, See. 
14 +' chromosomes. 
See remarks below. 
lasicpetala, Bart. ? 
Oe. stenomeres , Bart. 
Bartlett, 1915 
Chromosomes not 
counted. 
saligna, de Vries 
lata 
unnamed 
Oe. biennis , Chicago, de V. 
Oe. grandifiora x biennis 
Oe. rubricalyx x Hcwettii 
de Vries, 1916 
Davis, 1913 
Here recorded 
5) 
For purposes of interpretation we may consider (1) the parallel mutations 
(lata) which have appeared in Oe. Lamarckiana , biennis , suaveolens , also as 
mutations from 14-chromosome mutants, and in various hybrids; (2) the 
various 15-chromosome types which have arisen directly from Lamarckiana. 
The now widely adopted conception of parallel mutations was based upon the 
fact (Gates, 1912 a) that Oe. Lamarckiana mut. lata and Oe. biennis mut. 
lata were corresponding types resulting from the same kind of germinal 
change in different species. A partial list of parallel mutations in Oenothera 
has been published elsewhere (Gates, 1921 ). It has long been recognized 
that lata is in many respects intermediate between Lamarckiana and gigas 
although it has but one extra chromosome. Van Overeem ( 1922 ) shows 
that the papillary cells of its stigma are conspicuously larger than in 
Lamarckiana , and concludes that in lata there is a lack of balance 
between cell size and turgor, the lack of turgor accounting for the habit 
of the plant. 
The question of the relationships between the various mutants with 15 
chromosomes is a very difficult one. In the first place, we may eliminate 
from present consideration all such forms arising from different species than 
Lamarckiana or from hybrids between forms belonging to two distinct 
species. Such cases of course all arise through a chance irregular meiotic 
division during the distribution of the hybrid differences in the germ cells 5 
as was originally explained in the case of lata rubricalyx (Gates, 1914 ). 
This leaves us to consider the various 15-chromosome forms arising from 
Lamarckiana and its mutants. In various combination mutations, such as 
nanella lata and simplex lata , the explanation is evidently similar to that 
given above. If we examine the 15-chromosome forms arising directly 
from Lamarckiana , we find in the first place the following from the experi¬ 
ments of deVries: lata , albida , scintillans , oblonga , which are all widely 
different and have long been known, and pallescens, L^actnca, liquid a, and 
cana , which are closely related, are more like Lamarckiana and have been 
discovered more recently (de Vries, 1916 ). The chromosome number in 
cana has apparently not been actually counted, but its genetic behaviour is 
exactly like that of the other forms with 15 chromosomes, leaving no doubt 
