Benedict: New hybrids in Drvopteris 45 



sporangia attain full size, in abnormal, granulated spores. Only 

 in a few mounts out of scores examined have any normal spores 

 been seen, and in these few instances their presence may have been 

 accidental. But as In hybrids generally, it is probable that the 

 sterility is relative rather than absolute, and we may expect occa- 

 sionally to find fern hybrids capable of reproducing by spores. 



Correlated with the sterility is usually a greater vegetative ac- 

 tivity. This may be expressed merely in the development of 

 larger plants, or it may take the form of abnormal fronds in which 



m 



some parts are greatly expanded while others remain of ordinary 

 size or even abort. Such irregular fronds are of frequent occur- 

 rence in D. cristata x margmalis but are by no means invariable, 

 as many plants are found in which all the fronds are symmetrical. 

 Occasionally this irregularity is so marked as to obscure the 

 general resemblances of the suspected hybrid, and in such cases, 

 unless the identity of the parent species can be established beyond 

 doubt by means of critical characters, a positive identification may 

 be impossible. In this connection it should also be noted that 

 irregular plants which are to be explained 'as due to ecological 

 conditions or as sports rather than as hybrids, are not unusual. 



3. In distribution, Dryopteris hybrids are rare or occasional in 

 damp woods with the parent species. The general occurrence of 

 hybrids has been doubted because of the presumed diflficulty of the 

 actual process of hybridization but the presence of numerous plants 

 of D. cristata x marginalis in some especially favored localities is 

 evidence that the difficulty may not be as great as has been im- 

 agined. The immediate presence of the parent species is not a 

 necessity since fern plants are often long-lived and the greater vigor 

 of the crosses might render them resistant to conditions sufficiently 

 adverse to destroy the parent species. 



Following are descriptions of hybrids already noted as new : 



Dryopteris Clintoniana x spinulosa hyb. nov. 



In habit resembling D, Clintoniana, the rootstock horizontal, 

 the fronds of two sorts: (i) juvenile and sterile, and (2) mature 

 and usually soriferous : mature fronds tall, about 70 cm. long ; stipe 

 light yellow above, dark brown below, clothed with thin pale brown 

 scales ; lamina oblong, acuminate, 30-40 cm. long, by 16-20 cm. 

 broad, once pinnate, the rachls distinctly winged in the upper fourth ; 



