126 THE BRITISH FERNS. 
they are forked. Indusium membranaceous, orbicular, peltately 
attached. Spore-cases numerous, dark-brown, roundish-obovate, 
stalked. Spores slightly muriculate. 
Duration. The caudex is perennial. The fronds are persistent 
through the winter and the following summer, though sometimes 
damaged by severe frosts. The young fronds grow up in May. 


The division of the bipinnate aculeate Ferns into three species, 
i. e. lobatum, aculeatum, and angulare, Mr. Newman observes,* 
probably originated in an error of nomenclature, and he arrives at 
this conclusion from a careful consideration of the original descriptions. 
* Linnsus considered the plants referrible to single species to which 
he gave the name aculeatum. Hudson, observing the great discrepancy 
between the extreme forms, divided them into two species, calling the 
rigid and least divided form /obatum, and the lax and most divided 
form aculeatum. Kunze adopted these names; but Willdenow had 
redescribed the species, transferring the name aculeatum to Hudson's 
lobatum, and giving the new name of angulare to Hudson’s aculeatum. 


SS 
Thus the three names were not intended to represent three objects ; 
a conclusion inadvertantly adopted by Sir J. E. Smith. There is 
now a growing disposition to reunite them as one species.” It is 
however doubtful whether Linneus knew anything of angulare, 
though there is hardly room to doubt that he included the other two 
forms under aculeatum, which is the view which both ourselves and 
Mr. Newman have adopted. 
Though P. aculeatum is often difficult to distinguish from our 
next species P. angulare, yet viewing the British forms alone, it 
appears to be really distinct. Indeed, if these plants are not 
distinct, a series varying through every gradation from the pinnate 
lonchitidoides to the tripinnate forms of angulare must be united, 
and all hope of defining a species would then-be at an end. While 
admitting the difficulty of discriminating between some forms, espe- 

cially exotic ones, of these two species, we may endeavour to 
point out how they may generally, with tolerable certainty, be 
known from each other. 














* Newman, History of British Ferns, 3 ed. 112. 
See 



