1910] HOYT—FERTILIZATION IN FERNS : 351 
on a sufficient number of closely related species, and the results in 
most cases are not sufficiently conclusive to settle the question. But 
these experiments do show that not every combination of egg and 
sperm will yield a hybrid. Such a result is to be expected, but in 
view of the supposed cross between Camptosorus rhizophyllus and 
Asplenium platyneuron, it cannot be assumed without proof. A 
priori, we should expect hybrids to occur in some cases, but the 
fact remains that in the two investigations on the subject where known 
elements have been used, only negative results have been obtained. 
B. Fertilization 
It is well known that fusion will occur between the sexual cells 
of different species in some cases and will not occur in others, but 
few attempts have been made to determine in the cases where fusion 
does not occur the point at which the processes stop and the conditions 
causing this cessation, or to induce fusion in cases where it does not 
occur under normal conditions. 
In ferns the process of normal fertilization has been described 
by StrasBurGER (48), SHAW (42), VOEGLER (51), THOM (50), 
Mortier (34), CoNARD (4), and YAMANOUCHI (53). PFEFFER (36) 
and VOEGLER (51) obtained entrance of the sperms of one species 
into the venters of other species in every combination tried. VOEGLER 
attempted to follow in more than roo living prothalli the movements 
of sperms which had entered the venters of other species. In every 
case, although the sperms came into contact with the eggs, they were 
unable to enter, and finally ceased their movements, or after several 
attempts to enter the egg left the archegonium. Presumably the 
phenomena observed were the same as those described below. 
In the present investigation attraction of the sperms and their 
entrance into the venter has been obtained in every combination used, 
and in several cases the living sperms have been observed and their 
movements followed within the venters of the same species and of 
different species. In most cases the sperms were seen as an actively 
Moving mass lying against the egg on the side turned toward the 
archegonial neck, the so-called receptive spot. The egg looked round 
and turgid. The individual sperms, when distinguished, had their 
anterior ends apparently in contact with the egg and were lashing 
