104 
H. H. BARTLETT 
Oe. Lamar ckiana, quite regardless of whether the pollen was derived 
from the heterozygous mutation or the homozygous parent species. A 
partial elimination of lata-eggs would explain the deviation from the 
expected i : i ratio, for the mutational form rarely constitutes a full 
half of the progeny. The pollen of Oe. lata is so much more highly 
defective than the ovules that this hypothesis seems not an improbable 
one. Gates and Thomas^ have shown that in Oe. lata the cytological 
facts are in accord with such an explanation. The somatic number of 
chromosomes is 15, whereas in Oe. Lamarckiana it is but 14. Oe. lata 
therefore produces two classes of gametes, with 8 and 7 chromosomes, 
respectively. If two 7-gametes fuse, we have Oe. Lamarckiana; if a 
7-gamete (presumably male) fuses with an 8-gamete (presumably 
always female) we have Oe. lata. Plants with 16 chromosomes have 
not been found. From this fact, and the data in regard to inheritance, 
we must assume that the male 8-gametes are eliminated. 
There is clearly no reason why mutations which follow the lata- 
type of inheritance should not be viewed as progressive in their nature, 
even though they exist only as heterozygotes. Thus far only three such 
are known, Oe. lata, Oe. scintillans and the new Oe. stenomeres mut. 
lasiopetala. 
Oe. stenomeres mut. gigas, mut. nov. 
This rare mutation was found in the same progeny which included the 
first Qx^mpXeoi mut. lasiopetala. Sofaronly onespecimenhasappeared. 
In the former paper (I.e., p. 236) it was merely referred to as a mutation 
with ' ' very large, thick buds and short, thick fruits. ' ' It was even then 
thought to be a gi^a^-mutation, but was not named because a chromo- 
some count had not yet been made. Mr. E. G. Arzberger has now 
found the chromosome number to be 28. Cytologically and mor- 
phologically there is perfect analogy between Oe. stenomeres mut. 
gigas Bartlett and Oe. gigas de Vries. Each is more persistently bien- 
nial than its parent form and has thicker, broader leaves, stouter stems, 
larger buds, thicker fruits, 4-pointed instead of 3-pointed pollen, and 
twice as many chromosomes. Each is characterized by a strongly 
rosuliferous rather than freely branched main stem, and bears its 
branches mainly in the axils of the rosette leaves. Each is marked by 
a greater range of variation than its parent form, in that it gives rise 
5 Gates, R. R. and Thomas, Nesta. A Cytological Study of Oenothera mut. 
lata and Oe. mut. semilata in Relation to Mutation. Quart- Journ. Micr. Sci. 59: 
523-571. 1914- 
