GENETICS: B. M. DAVIS 
361 
to determine for Oenotheras the ratio of fertile seeds to the structures 
that in outward appearance cannot be distinguished from seeds but 
which contain no Kving tissue or only a small amount of endosperm, 
with an embryo, if present at all, so small or abnormal that it cannot 
produce a seedling. We are indebted to 0. Renner^ for the first de- 
tailed investigation of the sterile seeds of an Oenothera and for the formu- 
lation of a most interesting hypothesis as the result of his studies on O. 
Lamar ckiana. 
During the past winter I have tested the seed fertility of fifty species, 
races, or hybrids of Oenothera and as a result of these experiments I 
have become convinced that genetical research in this group must in 
the future adopt methods that will ensure a rapid and complete germi- 
nation of the viable seeds and at the same time conserve the sterile 
seeds or undeveloped seed-like structures for examination. Such 
methods will require that seeds be germinated in some convenient 
receptacle and subsequently be set in earth leaving as a residue within 
the receptacle all sterile structures. 
The method employed this winter is briefly as follows: In a Petri 
dish 3f inches in diameter was placed a pad of circular filter papers 3 
inches across and about J inch thick. The dish, cover, and paper pad 
were then sterilized by heat after which boiled tap-water was added 
in such quantity that the thoroughly soaked paper pad lay in the center 
of the dish surrounded by water. The seed-like structures were then 
spread over the surface of the pad and the dish covered. The seeds, 
therefore, lay on a very wet surface and in a moist chamber; more water 
was added when evaporation materially lowered the level in the dish. 
The tap- water was boiled to avoid the introduction of algae; fungi 
appeared in some of the cultures but apparently found the seed coats 
an unfavorable substratum for they grew very little; bacteria were like- 
wise not troublesome. 
The Petri dishes with seeds were placed in shaded parts of the same 
hot house with cultures sown in earth and were thus under similar 
conditions as to temperature. The possible germination within the 
dishes was always very much more prompt than for a similar sowing 
of seeds in the earth and proved to be complete when sufficient time was 
allowed. The advantages of Petri dishes as receptacles are those of 
convenience in the removal of germinated seeds and in the collection 
and examination of the residue. Petri dishes are also readily stacked 
and upon labels over the covers may be recorded the data of the 
experiment. 
The rate of germination in the Petri dishes under the conditions of 
