FILICES. 



1047 



common in Europe and Russian Asia, from northern Spain and Italy to 

 the Arctic regions. Abundant in Britain. Ft. summer and autumn. 

 More than twenty varieties of this species have received distinct names, 

 and three at least have been considered as species, but have no tangible 

 characters to separate them. 



8. Rigid Shieldfern. Aspidium rigidum, Sw. (Fig. 1274.) 

 (Eng. Bot. Suppl. t. 2724. Lastrea, Bab. Man.) 



Very near the broad S., of which it has 

 the deeply toothed or pinnatifid, oblong- 

 lanceolate segments, but the frond is 

 stiffer and not so broad, and the sori are 

 much larger, the two rows often occupy- 

 ing nearly the whole breadth of the seg- 

 ments, their indusiums conspicuous and 

 persistent as in the male S. and the 

 crested S. 



In rocky situations, especially in lime- 

 stone districts, in temperate Europe, 

 from the Pyrenees to Norway, extending 

 eastward into central Asia, and in North 

 America. In Britain, chiefly in the lime- 

 stone districts of northern England, but 

 said to occur also in western England 

 and Ireland. Fr. summer and autumn. 

 Some botanists are of opinion that this 

 and the two preceding species are but varieties of the male 8., into which 

 they certainly appear (when seen growing in profusion) to pass, through 

 numerous intermediate forms. 



1274. 



VIII. SPLEENWORT. ASPLENIUM. 



Fronds (in the British species) once, twice, or thrice pinnate or 

 forked, usually rather stiff, though slender, and often small. Sori ob- 

 long or linear, on the under surface, usually diverging from near the 

 centre of the segments, covered when young by a membrane or in- 

 dusium, which opens cutwards, being attached lengthwise along the 

 outer side. 



Widely dispersed over the globe, and one of the most natural among 

 the large genera of Ferns, for although a few of the larger species are 

 scarcely to be distinguished from some species of Aspidium and Poly- 

 pody, except by the sori, the great majority have a peculiar dark-green, 

 smooth appearance, which makes them easy to recognize. 



