268 Shaw . — The Fertilization of Onoclea. 
the ripe archegonia. Many of the plants of the culture of 
November 3 were ready for fertilization in less than two 
months. The soil of this culture was poorly mixed, so that 
the plants on different parts of its surface did not develop 
uniformly, but they were quite capable of producing embryos. 
The first series (No. I) of O. Struthiopteris was begun 
December 29, 1896. Three lots were fertilized in as many 
ways : lot 1 included prothallia which were removed from 
the soil, fertilized under the microscope, and replaced on 
moist soil in watch-glasses ; in lot 2 were plants which were 
removed from the box with soil attached to their root-hairs, 
and fertilized by flooding them in watch-glasses, where they 
were drained and left ; lot 3 was fertilized by flooding the 
prothallia on the soil. Others were treated like the first 
lot, except that they were not passed under the microscope. 
Ten specimens from lot 2 were placed in water under the 
microscope eight days afterwards, and archegonia opened on 
only two of them. This indicated that the formation of 
mature archegonia had ceased on most of the prothallia 
of this lot, probably because the fertilization was effective. 
Plants from different lots were fixed on each successive day 
for ten days. Specimens representing the whole series were 
sectioned, but no embryos were found. 
On February 15, 1897, the culture of November 17, 1896, 
w r as well advanced. The prothallia were the greenest and 
most regularly formed of all that had been raised. The box 
was placed in a horizontal position, and filled for about fifteen 
minutes with water enough to flood half of the culture. The 
box was then drained and returned to its original position 
so as to minimize the geotropic disturbance. A series (No. 
Ill) was then taken from the box after varying intervals 
up to nine days and twenty-three and a half hours. When 
the oldest of these were sectioned, one egg with the nucleus 
in the anaphase of the first division, and another with the 
first division complete, were found. In the next younger 
lot of this series, which was six days and nineteen hours old, 
no dividing egg or embryo was found. With this clue to 
