961 
Oenothera Lamarckiana and O. gig as. 
mentioned above may have important bearings on the problem of the 
origin of such a type as gigas , for the origin of gigas was possibly concerned 
with the appearance of a tetraploid condition in the nuclei of Lamar ckiana , 
and suggests an interesting line of experimental study upon this latter form. 
It is of interest to compare gigas with Lamar ckiana in view of the fact 
that the only cytological difference so far known concerns simply the 
presence in the former type of a double set of the same chromosomes which * 
are present in the latter. Oenothera gigas is conspicuously larger and 
more robust in almost all of its parts than its parent Lamar ckiana. The 
seeds and seedlings are larger ; the rosettes are frequently much larger ; the 
stems are thicker and stronger; the foliage leaves are broader; the buds 
are larger, as are all of the flower parts ; the capsules are much thicker, 
although proportionately somewhat short. The height of gigas is, how¬ 
ever, generally not so great as, or no greater than, that of Lamar ckiana. The 
differences between the two forms thus concern the relative proportions 
of the organs. There are no obvious characters present in one plant that 
are not found in the other, and this would be expected since the inheritance 
is through chromosomes which are qualitatively similar. 
Nevertheless, while the differences between gigas and Lamar ckiana 
may depend chiefly on the greater vegetative vigour or luxuriance of the 
former type, it is clear that the expression varies in the different organs, 
since the results are not uniformly proportionate throughout the organiza¬ 
tion of gigas. That is to say, gigas is not a giant form of Lamar ckiana 
proportionately larger in all of its parts, but it has distinct characters of 
its own due to different comparative relations in the form and measure¬ 
ments of its organs. Gigas , therefore, does not bear the same relation to 
Lamarckiana as the giant form of Primida sinensis seems to bear to the 
ordinary form, from which it appears to differ simply in the greater size 
or luxuriance of its parts. In this case as reported by Gregory (’ 09 ), the 
giant has the same number of chromosomes as the smaller parent form, 
but the cells and nuclei in the tissues studied were found to be slightly 
larger. These differences in size were relatively very small as compared 
with those between the nuclei and cells of gigas and Lamarckiana, and the 
two cases are evidently not of the same class. The large form of Primida 
sinensis is apparently a true giant variety of the parent type, while gigas 
is a progressive mutant, its peculiarities being clearly sufficient to separate 
it as a distinct species from L amarckiana. 
The conclusion seems unavoidable that^^w arose with its peculiarities 
fully developed as the result of profound changes in the germ-plasm of its 
parent Lamarckiana , and as far as cytological evidence goes, the doubling 
of the chromosome count was the most obvious cause of the changes. In 
this germinal modification lay the basis for the sudden appearance of 
a sharply marked mutant more distant from any possible parent wild species 
