Shaw. — The Fertilization of Onoclea . 267 
division of the egg found. Finally, a double series was begun 
on May 1 1 by flooding some of the prothallia in the saucers 
in which they had grown, and by transferring others from 
the soil to the surface of distilled water, as had been done 
with the specimens of all the previous series. Those left 
on the soil were flooded for a time sufficient for the impreg- 
nation of all the mature eggs and then drained. Specimens 
from the soil were fixed at the end of every twenty-four 
hours for fifteen days, and from the water at the same times 
for the first seven days. It was thought, naturally enough, 
that seven days would be more than enough for the develop- 
ment of embryos, and it was intended that this double series 
should show whether the growth of the embryos was pre- 
vented or retarded by removing the prothallia from the 
surface of the soil and leaving them on the surface of distilled 
water. The material was preserved in alcohol, and when 
sections were made, in the following September, no embryos 
were found in the prothallia fixed at the end of seven days, 
and the writer made the mistake of not sectioning a large 
number of those from the fifteen-day period. 
Dr. Campbell then obtained from Michigan spores of 
O. Struthiopteris , and several cultures were started, some in 
the saucers used in the preceding season, some in a box 
on soil already in the laboratory, and some in a similar 
box on a fresh supply of black soil, a mixture of leaf mould 
and adobe. The plants in the saucers were not well lighted, 
and for this and other reasons they did not grow so rapidly 
or uniformly as those in the boxes. Each box was covered 
with a pane of glass. The spores on the old soil were sown 
on November 3, and the box was inclined at an angle of 30° 
before a deep south window about 60 cm. distant. Those 
on the fresh soil were sown on November 17, and placed 
in the same way before an east window. The tilted position 
of the boxes secured a better illumination, and kept the 
surface of the soil well drained. It also prevented the water 
which condensed on the inside of the glass cover at night 
from dripping on the mature prothallia and thus fertilizing 
