Proceedings of the Section of Biology 173 



that our Dryopteris boottii (Tuck.) Und. has often been referred 

 to the hybrid long known in Europe and described by Milde as 

 Aspidium spinulosum X cristatwn. He mentioned Dryopteris 

 cristata X marginalis and the bigeneric hybrid Asplenium 

 ebenoides as well known examples of hybrids among ferns. He 

 referred to Miss Margaret Slosson's experiments in which she 

 succeeded in crossing the prothallia of the parent species and pro- 

 ducing Asplenium' ebenoides and Dryopteris cristata X marginalis, 

 thus proving these to be hybrids. These were the only native 

 American fern hybrids known until recently ; except, possibly, 

 Asplenium pinnatifidum, which has been supposed by some to be 

 a hybrid. He next made a few remarks on the recent paper 

 " New Ferns described as Hybrids in the Genus Dryopteris," in 

 the Bull. Torrey Club 35: 135-140. 20 Ap. 1908. In connec- 

 tion with Asplenium ebenoides he reviewed some of the main 

 points in his paper on this fern written some years before (Bot. 

 Gas. 30: 410-415. Dec. 1900). One of the main points brought 

 out in this connection is that although sterility is in general a 

 characteristic of hybrids it may not be persistent in the case of 

 plants long established in a certain locality. Thus, for example, 

 Asplenium ebenoides was found growing in abundance at Havana, 

 Hale Co., Alabama, and this could not be well accounted for 

 except on the supposition that the fern was fertile in this locality. 

 This idea of hybridity clears up some of the difficult questions in 

 regard to the identity of many specimens of ferns that have been 

 collected and many that have been met with in the field. 



Dr. Philip Dowell replied to some of the questions raised. In 

 connection with the question whether the chances for hybridiza- 

 tion are better in the north than in the tropics it should be kept 

 in mind that some species seem to show greater tendency to 

 hybridize than do others. To the question whether the recent 

 work on hybrid ferns be a result of more intensive work in the 

 field, he replied that his own results had been obtained as un- 

 doubtedly due to intensive field study. Occasional specimens of 

 hybrid ferns were found in the larger herbaria, but many more 



