PHYSIOLOGICAL ASPECTS OF FERTILIZATION AND 
HYBRIDIZATION IN FERNS? 
W. D. Hoy? 
(WITH TWELVE FIGURES) 
The present investigation was undertaken as the first part of a 
study of the physiology of cell fusions. The first thing to be done in 
such a study is to determine what cells will fuse under normal con- 
ditions; the next step is to discover, in cases where fusions do not 
normally occur, the point in the events occurring in normal fusions 
where the process has stopped, and, so far as possible, the conditions 
causing the cessation of this process; the third step will be to discover 
conditions permitting the fusion of cells which will not fuse under 
normal conditions. 
The results obtained in the present study will be considered under 
three heads: (x) under the heading Hybridization the evidence 
bearing on the occurrence of hybrids in ferns will be considered, and 
the results of many attempts to induce experimentally hybridization 
between many species and several genera will be given; (2) under the 
heading Fertilization it has been possible to show, in some of the cases 
where fusions have not been obtained, at what point in the progres 
of normal fertilization the process has stopped, and to indicate some 
of the factors determining this cessation; (3) under the heading 
Movements and reactions of sperms will be given the observations 
made to determine whether the reactions of fern sperms are of the 
same kind as those described for protozoa or whether they are of a 
different kind. : 
A. Hybridization 
I. HISTORICAL AND CRITICAL 
A fern hybrid was described as early as 1837 (29), when th : 
of the spores and the prothallus were still unknown and the ideas 
concerning reproduction among pteridophytes were still shadowy: 
« Contributions from the Botanical Laboratory of the Johns Hopkins University, 
No. 13. 
Botanical Gazette, vol. 49] [34° 
e nature 
