G^]N0THE1?A MUT. LATA AND (E. MUT. SEMILATA. 523 
A Cytological Study of CEnothera mut. lata 
and CE. mut. semilata in Relation to Muta- 
tion. 
By 
K. Kiliriflos Oates, Pli.D., F.L.S., and 
J\esta Thomas, B.Se. 
With Plates 35, 36, and 37, and 4 Text-figures. 
Introduction. 
The special interest which attaches to the genus CEnothera 
at the present time arises from the description by de Vries of 
the mutation phenomena in these forms. The observations 
of de Vries have subsequently been confirmed by various 
investigators, but there has been much difference of opinion 
concerning the nature, causes and significance of the 
mutations themselves as they occur in CE.Lamarckiana and 
CE. biennis. 
The two main views which have been expressed regarding 
the origin of the mutants have been (1) that they arise 
througli a germinal change or a mutation in the de Vriesian 
sense, (2) that they are all merely re-combinations of Mende- 
lian characters already present in the parent form. 
One of us (Gates, 1909a) was able to show that in the 
rnutant, CE . gigas, the cells are of gigantic size, and that this 
explains most of its peculiarities. The giantism of the cells 
is associated with a doubling in the chromosome content of 
their nuclei (Lutz, 1907, Gates, 1908b). CE. mut. gigas is 
therefore a tetraploid species, having 28 instead of 14 
chromosomes, and in this respect it resembles many wild 
species in Nature (see Gates, 1913b). 
