344 BOTANICAL GAZETTE [May 
as hybrids, Dryopteris cristataXD. marginalis and Asplenium 
platyneuronXCamptosorus rhizophyllus (the well-known Asplenium 
ebenoides). These results are almost convincing, but do not place 
the subject beyond question. Cutting does not, in every case, 
separate the antheridia and archegonia; then, too, the prothalli 
formed branches and produced new sexual organs, so that, in the 
case of Asplenium platyneuron and’ Camptosorus rhizophyllus, many 
plants of each species appeared together with a few of the supposed 
hybrids. These experiments, therefore, are open to the objection 
raised by Miss Stosson (46) herself against the method of planting 
spores or whole prothalli together. They prove that the offspring 
come from one of the species planted, but do not prove whether this 
is by hybridization or some other method of variation. So far as 
the author is aware, no experiments have been made to prove that 
Asplenium platyneuron may not at times give rise to Asplenium 
ebenoides. Specimens of Asplenium’ pinnatifidum observed by 
COPELAND (5) approached, in their variable characters, Camptosorus 
rhizophyllus and bore a striking resemblance to Asplenium ebenoides, 
although no Camptosorus was found in the immediate neighborhood. 
Drvuery (9) observed variation in plants of Cryfomium jalcatum 
and Lastrea pseudo-mas cristata produced apogamously. In another 
experiment he obtained from spores of a single plant of Athyrium 
plumosum offspring showing almost as many differences in the leaves 
as were found by Lowe in his “plants with multiple parentage.” 
In a recent article LEavitr (23) has described the origin, through 
vegetative variation, of the Pierson and Whitman ferns, and has 
described the particular type of variation called “homoeosis”’ in 
_ ten species of wild ferns distributed among six genera. | 
It is clear that other means than hybridization may produce 
variations among ferns, and that some of these variations may give 
characters approaching those which are supposed to belong to other 
species. This being the case, we must regard as unproved all cases 
of supposed hybridization founded on structural characters of the 
sporophyte. 
In the third class of evidence mentioned comes the work of VOE 
(51). This is the one case of experimental studies on hybridization 
in ferns where the experimenter attempted to work with known units; 
GLER 
