348 BOTANICAL GAZETTE [MAY 
cruciata, and it was assumed that such strains would behave as 
true species in all characters not related to the differentiating marks 
of the petals. It must be conceded, therefore, that the cross of 
these two forms may be treated ‘‘as though-it were the combina- 
tion of forms within the same species, which have similar germinal 
constitutions” (Davis, op. cit. p. 117). 
But the most clear and simple way of obviating this whole 
objection is evidently to sow seeds of O. biennis of pure descent 
upon the same large scale as in the former experiment. This has 
been done, and a dwarf and a semigigas form have been produced 
by this pure line, besides some other mutations.’ They had the 
same characters as the former ones, and now provide us with the 
“strong support” asked for by Davis. Moreover, they show that 
his choice of O. biennis for a proof of the assertion that mutability 
might be produced by crossing immutable species was a most 
unhappy one. 
The second condition for success in this kind of work is, as has 
been stated, the purity of the types to be crossed. As already 
quoted, Davis assumes that a cross between two very distinct 
evolutionary lines may give a hybrid with marked modifications of 
germinal constitution. This may be applied to his choice of the 
type which he calls O. grandiflora, and which he has made the 
other parent of his initial cross. He got his seeds from Dixie 
Landing, Alabama, a locality where BARTRAM had discovered 
O. grandiflora about a century ago. He assumed them to be of the 
pure species, but a culture which I made in my garden from seeds 
kindly supplied to me by Mr. Davis proved to be a mixture, and 
thereby threw a distinct doubt upon the purity of the station. 
For this reason I visited Dixie Landing in September 1912, and had 
the good fortune to be accompanied by Mr. H. H. BARTLET, 
of Washington, well known for his systematic researches among 
the wild species of this group. We found the station in a most 
desolate condition. A small-flowered species, O. Tracyi, in almost 
all respects different from O. grandiflora, had migrated into the same 
old cotton fields and mixed everywhere with the species of Bark- 
*Sromps, Tu. J., Parallele Mutationen bei den Oenotheren. Ber. Deutsch. Bot. 
Gesells. 30: Heft 3, 1914. 
