1910] HOYT—FERTILIZATION IN FERNS 341 
In this case two species, Gymnogramme chrysophylla and G. calo- 
melanos, were growing near each other; spores of the former, when 
planted, produced ferns which were supposed to show characters 
approaching those of the other species. This case is described here 
because it shows a tendency which has persisted among students of 
ferns to the present day, that of describing as hybrids plants which 
are supposed to show intermediate characters, without sufficient 
evidence as to the real origin of these plants. 
All later studies of fern hybrids fall into three groups. The first 
includes the numerous cases where plants have been found in the 
field or greenhouse differing in some respects from the characters 
considered as typical for one species, and supposedly approaching 
in these respects the characters considered as typical for another 
species. The second group includes those cases where spores, pro- 
thalli, or portions of prothalli of two or more species have been planted 
together in the hope that cross-fertilization might occur, and plants 
arising from these cultures showing supposedly intermediate char- 
acters have been described as hybrids. The third group is composed 
of a single case where sperms of a known species were presented 
to prothalli of another species bearing only archegonia, and the 
attempt was made to determine whether development of the embryo 
occurred or not. 
The first group is represented by the works of LUERSSEN (28), 
DRUERY (10, 11), Miss SLosson (45), HAHNE (15), Dowett (8), 
BENEDICT (I, 2), and others. FOocKE (14) lists the supposed 
hybrids described before 1881, and concludes that, except in the 
genus Gymnogramme, all are doubtful. It is not evident why FockE 
excepts Gymnogramme in this conclusion. 
The reasons for regarding the kind of evidence considered by 
these authors as sufficient to prove the hybrid nature of the supposed 
Crosses are given by BENEDICT (2) ina recent paper. These reasons are 
(1) the intermediate character of the supposed hybrid, (2) its sterility, 
abnormality, and greater vigor as compared with the supposed parents, 
(3) its occurrence being found only occasionally and then usually 
with the Supposed parents. BENEDICT states, however, that “irregu- 
lar plants, which are to be explained as due to ecological conditions 
or as sports rather than as hybrids, are not unusual. The immediate 
