rOLYPODIACE.E. 339 



tinguishaWe from it by tlie less scaly rhachis and much obttiser auricles of the 

 pinnee. 



Group of Polystichum tripteron PR. 



Species belonging to this group having simply pinnate fronds with pinnate 

 lowest pin nm, which are longer than the others and are arranged horizontally, 

 were previously two in all ; one is the Japanese species, P. tripteron PR. and 

 the other, the Formosan, P. Hancocldi DIELS. In my last excursion to Formosa, 

 I paid special attention to this group of ferns and found several new species 

 which are very similar in appearance yet separable in details. Of all the species, 

 P. tripteron PR. is the most easily distinguishable from the others in having 

 narrowest pinnre with by far the sharpest teeth, in the thinnest texture and in 

 the cellular structure of the scales. PolysticJium longistipes HAYATA and P. 

 Hancocldi DIELS are separable from the other species by the very long stipes 

 which nearly equal the fronds in length. P. siinplicipinnum HAYATA and P. 

 i/feyamense MAKING differ from the others by the lowest piniias which are 

 nearly the same as the other pinmw or slighly longer and scarcely pinnate. 

 As can be considered from the following key, the distinction between each two 

 of the species can not be very clearly given in verbal expression and the 

 difference itself is really very small, so that even to accurate observers it would 

 be difficult to recognize the species proposed by me. I myself am pretty 

 sure that many botanists will be apt to render my species to varieties of the 

 oldest species Polystichum tripteron PR. As it is a veiy difficult task and 

 depends to a greater extent upon personal opinions, to decide whether they 

 should stand each distinct or should be regarded as varieties of some one 

 species, I shall at present leave the question entirely to the readers. 



Key to the species of the group represented by Polystichum tripteron PR. 



A. The lowest pinna? are very much longer than the others and are usually 

 once more pinnate. 



a. Fronds much longer than the stipes. 



a. pimife more than 2 cm. long, more or less recurved after /-^-''-form, 

 more sharply toothed. Polystichum tripteron PR. 



