ON THE VARIETIES OF BRITISH FERNS, ETC. 
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serrated. Aspidium cristatum has been confounded with a small state of this 
plant, but may easily be distinguished by its narrower frond, and short u obtusely v 
ovate-oblong pinnae, the segments of which are acutely, sometimes doubly serrate. 
Aspidium rigidum. 
A. rigidum , Brit. Flo . (Hook.), 3rd Ed., p. 450; 4th Ed., p. 385. 
“ “ Brit. Ferns and Allies (Francis), p. 33, pi. 2, fig. 10. 
Distinct as this may appear to those who have seen the Yorkshire plants, its 
characters are far from being well known by those who have not. 
Mr. Francis is not exactly correct, I think, in stating that its “ alternate pinnae 
would be amply sufficient to distinguish” it; since I have a specimen in which 
the lowest pinnae are almost exactly opposite, nearer so than in A. spinulosum , 
after which they become, by degrees, alternate. I have also one in which the 
lowest pinnae are above an inch apart, the second pair half an inch, the third 
and succeeding pairs to within three inches from the top opposite; after which 
they become alternate, the right-hand pinnae being the lowest at the bottom of 
the frond, and the left-hand one at the top; in others they are alternate, others 
are different still, but these are sufficient to show that the relative position of 
the pinnae is not an “ amply sufficient” diagnosis. It may, however, always be 
easily distinguished by its narrow oblong pinnae, the large indusium, which is 
seldom present on the lower ones, and the distinctly bi-dentated pinnules. 
A. cristatum has been mistaken for this and the allied species spinulosum , from 
both of which it is sufficiently distinct in its simply pinnate frond and broad 
pinnae. 
Aspidium spinulosum. 
A. spinulosum , Brit. Flo. (Hook.), 3rd Ed., p. 451 ; 4th Ed., p. 386. 
“ “ Brit. Ferns and Allies (Francis), p. 34, pi. 2, fig. 11. 
“ “ With. Brit. Bot. (MacGilliv.), p. 381. 
There is still no little doubt as to what is to be considered as the true 
A. spinulosum; I have specimens from various places, named by several 
botanists of some eminence; but I must confess I can see in none of them 
diagnoses sufficient to distinguish them from the very variable A. dilatatum. 
The plant from Woolston Moss, only, appears to me to be distinct; and is easily 
recognised by its erect, long, and narrow frond, paler colour, somewhat rigid 
texture, and dark rachis; and I am happy in being able to state that this is 
also the opinion of my esteemed friend W. Wilson, Esq., who, in addition, men¬ 
tioned to me the small, entire edged involucres, and the absence of the auricle at 
the anterior base of the pinnules, as characteristics. 
