180 BOTANICAL GAZETTE [MARCH 
Let us now consider the production of new forms analogous to 
the mutations of O. Lamarckiana observed in allied species. The 
theoretical significance of these facts lies in the proof that any 
hypothesis to explain such phenomena on the ground of qualities 
which are special to LAMARCK’s evening primrose is to be con- 
sidered as wholly inadequate. 
The first instance of mutability shown by another species than 
O. Lamarckiana was the production of a dwarf by O. biennis 
cructata, a form which is now to be described as O. biennis var. 
leptomeres Bartl. This form was first discovered in 1900 by my 
son ERNST DE VRIEs in the sand dunes near Santpoort in Holland, 
where a single specimen of O. biennis bore linear petals, while all 
the surrounding individuals were normal O. biennis L. It had 
evidently arisen there by mutation.” From it a constant strain 
has been derived, which is still in cultivation. Among about 
600 plants of this variety a single dwarf arose in 1903.” It had 
all the marks of O. biennis L. combined with the stature of a dwari 
and the linear petals of the parent form. 
Shortly afterward Stomps discovered, in his cultures of hybrids . 
between this cruciata variety and the original species, another 
dwarf and, moreover, a new mutant type, O. biennis semigigas.* 
Both arose from guarded seeds without any intermediate steps, 
in the same way that the mutants of O. Lamarckiana are known 
to arise. They had cordate petals, the dwarf having in other 
respects the same characters as the dwarf of O. biennis leptomeres, 
and the semigigas having 21 chromosomes in its nuclei. STOMPS 
was the first to lay stress on these facts as a proof that mutability 
is not limited to O. Lamarckiana, and that, even if this latter 
species should have to be considered as a hybrid, mutability can- 
not be explained as a result of such a condition, since there is not 
the least doubt concerning the me site of O. biennis L.™ 
2 Die Mutationstheorie, Leipzig. 1900; se 
2t Pure seeds of this pure strain I shall be es ; a to any botanist interested 
in these questions 
2 Uber die Dave bes Mutationsperiode bei Oenothera Lamarckiana. Ber. Deutsch. 
Bot. Gesells. 33:3 905 
23 STOMPS, — - oe bei Oenothera biennis L. Biol. Centralbl. 32:532- 1912- 
4 Davis, B. M., Mutations in Oecnothera ates a Amer. Nat. shies 1913; 
also P; isL. Amer. Nat. 48:498-501. 19 
