1910] HOYT—FERTILIZATION IN FERNS 345 
it is, therefore, the only case where the results are trustworthy. 
VOEGLER presented the sperms of several species to the archegonia 
of other species and attempted to determine, by observing the living 
sperms after their entrance into the archegonium, whether they 
fused with the egg or not. The following combinations were tried: 
Dicksonia antarctica? X Nephrolepis davalloidess; Ceratopteris thalic- 
troides? or Nephrolepis davalloides? x Dicksonia antarcticaé, or 
Blechnum occidentales, or Gymnogramme Laucheanaz. In more 
than 100 cases of entrance, no fusion of the sperm with the egg was 
observed. VoOEGLER also presented the sperm of several species 
to the prothalli of other species bearing only archegonia, and, having 
replanted these, examined them after one or two days to determine 
by the appearance of the archegonia whether development of the egg 
ad begun or not. In all cases negative results were obtained; 
the archegonia had turned brown. 
There are obvious objections to the methods used: (1) there 
were not sufficient precautions to insure the absence of sperms on the 
archegonial prothalli; (2) observations on the surface can scarcely 
give certain conclusions about the fusion of sperm with the egg; (3) 
reliance is placed on the appearance of the archegonia after one or 
two days to determine whether development of the egg has occurred 
or not. Since in the two species where the time has been noted 
(SHAW 42, Conarp 4) the first division of the egg does not occur 
until after seven days, and since in this investigation the same time 
has been found to hold for other species, the method used does not 
seem beyond question. 
In this work of VoEGLER’s, the most reliable study of hybridization 
in ferns, all the results are negative. The author concludes that 
while hybridization is not thereby disproved, this must seldom occur 
and then only between certain species. 
2. METHODS 
Since the value of all work of this sort depends on knowing with 
certainty the origin of the sexual cells brought together in the archego- 
nium, it will be well to describe in some detail the methods used for 
insuring this in the present investigation. 
The prothalli used were in every case raised from spores. The 
