2 93 
Recent Papers on CEnothera Mutations. 
Lamarckiana and one which is furthermore present in varying 
degrees in various CEnothera races. The flowers of the Lamarckiana 
of De Vries are distinctly larger than those of the grandiftora forms 
from Alabama. The P x hybrids of Davis were, however, (as would be 
anticipated) intermediate in flower-size between grandiftora and the 
small flowers of biennis, the intermediacy also extending to all the 
other characters, though forms with larger flowers have been obtained 
in later generations. The reciprocal crosses were made, biennis x 
grandiftora yielding eight plants, seven of which resembled grandi- 
flora and were therefore patroclinous while one exhibited a certain 
amount of crinkling of the foliage. O. grandiftora x biennis, from 
the same parent individuals, produced twenty plants which were in 
two groups (twin hybrids), nine being granditiora-Uke in foliage and 
habit while eleven resembled biennis. 
Larger cultures of these P, and F 2 hybrids from fresh crosses 
were made in 1910 and 1911. The chief defect of these papers as 
descriptions of the hybrids is that the search for Lamarckiana- like 
plants among the offspring was allowed to overshadow the really 
more important general results of the crosses, since it was not to be 
expected in any case that Lamarckiana could have resulted from a 
single simple cross. In his last paper on these hybrids Davis virtually 
admits the correctness of this position. 
In 1907 De Vries first described twin hybrids (tceta and velutina) 
in the F 1 when Lamarckiana is used to pollinate biennis, Hookeri 
and other species. Notes on the anatomical features of these 
hybrids have been published by Andrews (1). The hybrid types 
both breed fairly true when self-pollinated. This hybrid behaviour 
has been confirmed by Gates (21) in the case of biennis x 
Lamarckiana, with full illustrations of the broad-leaved and narrow¬ 
leaved forms. Corresponding results were also obtained with biennis 
X Icevifolia. It therefore appears that in Lamarckiana and its 
mutant derivatives, including tcevifotia, the pollen grains are of two 
types, leading to a constant dimorphism in the Fj of the hybrids 
when these forms are used as male parent. In the reciprocal 
crosses, however, De Vries obtained a single constant race, 
indicating an absence of this type of dimorphism in the egg-cells of 
Lamarckiana, though these results have not been fully corroborated 
by the later investigations. 
This short review of the more recent hybridization results is 
necessarily very incomplete, but even a general summary of the 
data involved would be much too lengthy for the present purpose. 
The results show clearly, however, that several types of hereditary 
behaviour exist, and that these types depend upon the manner of 
origin and hence the relationship to each other of the various races 
and species concerned. Certain crosses give blended inheritance, 
others give alternation or segregation, others twin types unlike 
either parent, etc. A knowledge of the cytological conditions is 
necessary for an explanation of the hereditary behaviour of such 
mutants as gigas and lata, and also apparently of the results of 
certain double reciprocal crosses. In conjunction, these two classes 
of data furnish a consistent and rational view of very complex and 
sometimes apparently conflicting phenomena. 
In connection with the twin hybrids produced by Lamarckiana, 
Honing (25) has made an interesting comparison of Lamarckiana, 
