POLYSTICHUM ACULEATUM. 115 



the caudex, but upwards they diminish in size, and are much 

 smaller when the stipes has merged in a rachis. The caudex 

 has always a disposition to fix itseK on a perpendicular surface, 

 whence the fronds issue in a nearly horizontal direction, their 

 rigid habit almost precluding the possibility of their assuming 

 that graceful bend which is more or less observable in every 

 other fern similarly situated. The frond is variously divided, 

 but always pinnate : the pinnte also are variously divided : 

 when entire, as is usually the case in immature plants (see figs. 

 a a a, page 111), the fronds resemble those of the preceding 

 species, P. Lonchitis, from which circumstance the name of 

 Lonchitidoides has been applied to this form. "When the first 

 upper pinnule is separated from the body of the pinna, which 

 remains nearly entire (figs, h h), the plant is the Aspidium mu- 

 nitum of the continent ; at least, such is the opinion I gather 

 from the descriptions of Sadler and others : when the pinna is 

 a little more divided (figs, c c c), I suppose it to be the Polypo- 

 dium lobatum of Hudson, and P. aculeatum of Linneus ; and, 

 lastly, when the pinnule becomes quite pinnate at the base, and 

 even beyond the middle (fig. d), it is probably the Aspidium 

 aculeatum of Smith. I believe that no one who has watched 

 the plant with careful attention, has ever supposed these forms 

 to be more than varieties of a single species. The first upper 

 pinnule on each pinna is much larger than either of the others, 

 indeed, it is usually twice as large as the first lower pinnule ; 

 it points directly upwards towards the apex of the frond, but 

 owing to a certain convexity, which every division of the frond 

 in some degree possesses, its point is bent downwards, and 

 very frequently passes below and beyond the midrib of the pre- 

 ceding pinna ; the double series of these enlarged pinnules, 

 often amounting to more than twenty, has a very striking ap- 

 pearance : all the pinnules have a sharp spine at their extre- 

 mity, and several lesser spines at their edges, and each of the 

 enlarged superior pinnules is sHghtly auricled at its outer mar- 

 gin near the base, and the auricle, in those pinnules near the 

 base of the frond, has a very strong and distinct spine ; this 

 character extends to several of the other pinnules which most 

 nearly approach the stem, and these are generally placed on 

 short foot-stalks, whereas all the others are decurrent or united 



