454 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
plant was metaclinic and of the Oe. pratincola type. (See description of 
"Oe. biennis Chicago.'') 
Among the Fi hybrids of the reciprocal cross {''Oe. biennis Chicago'' 
X Oe. mississippiensis) , three plants of the mississippiensis type were pro- 
duced, while the rest were of the '' Oe. biennis Chicago" type, again showing 
matroclinic inheritance with a tendency toward metacliny. One mutation 
(of the latifolia type) was produced in one of these reciprocal crosses. 
All the plants of this pair of reciprocals were mildewed. No difference 
seemed to exist in the degree of susceptibility, and, because both parents 
are susceptible in the same degree, no other data could be obtained on this 
point. The F2 plants of both reciprocals were respectively of the same 
general type as the Fi, and all plants were susceptible. 
IV. Crosses between Oenothera mississippiensis (susceptible) and 
Oenothera pratincola ("Lexington C") (susceptible). 
The Fi and F2 generations of the cross Oe. mississippiensis X Oe. 
pratincola consisted of only one matroclinic type. All the plants were 
susceptible. 
The Fi of the reciprocal cross, Oe. pratincola X Oe. mississippiensis, 
was likewise of one general type, similar to Oe. pratincola, another illustra- 
tion of matroclinic inheritance. A part of the plants, however (28 out of 
icq), showed a distinct yellowish-green coloring and mottling of the leaves, 
in some cases going over to white, especially at the margins of the leaves. 
On this account the culture might be interpreted as consisting of very 
closely similar twin hybrids, both, however, resembling the pistillate parent 
{Oe. pratincola) in external characters, and probably only slightly different 
in genetical constitution. All the plants were susceptible, somewhat more 
so than those of the reciprocal. The F2 repeated the two types of the Fi, 
with some slight segregation in morphological characters, but all plants 
were susceptible. 
V. Crosses between ''Oenothera biennis Chicago" (susceptible) and 
Oenothera cinerescens (immune). 
All the plants of the Fi produced from the cross " Oe. biennis Chicago" 
X Oe. cinerescens were of the Oe. pratincola type. (See description of 
"Oe. biennis Chicago.") All were susceptible. No seeds were obtained by 
self-pollination, and consequently no F2 can be reported. 
The Fi plants of the reciprocal {Oe. cinerescens X " Oe. biennis Chicago") 
were all of the cinerescens type, with the exception of two metaclinic plants 
of the pratincola type. All cinerescens-\\k.e plants were immune, in both 
the Fi and the F2. Both metaclinic plants were resistant. 
VL Crosses between "Oenothera biennis Chicago" (susceptible) and 
Oenothera pratincola hyb. immunis (immune). 
The cross "Oe. biennis Chicago" X Oe. pratincola hyb. immunis gave an 
Fi generation of one type (similar to Oe. pratincola). All the plants were 
immune to mildew. No F2 was obtained. 
