564 



THE BOOK OF CHOICE FERNS. 



was found at Batli, and another at Louth, in Ireland ; but in such situations 

 as to justify the opinion that these were introductions. Its oblong-spear- 

 shaped fronds, 1ft. to l^ft. long and 4in. to 6in. broad, are borne on tufted 

 stalks 6in. long and clothed below with large, spear-shaped, light brown 

 scales. The largest leaflets, 2in. to 3in. long and lin. to l^in. broad, have 

 their leafits (pinnules) cut down nearly to the rachis (Fig. 137). The 

 fronds are of soft texture and upright habit, with their under- side slightly 

 glandular. The abundant sori (spore masses) are situated close to the 

 midrib, and are covered with a firm, prominent involucre fringed with 

 glands. — EooUr, Species Filicum, iv., p. 160; British Ferns, t. 16. Nicholson, 

 Dictionary of Gardening, ii., p. 443. Lowe, Ferns British and Exotic, 

 vi., t. 21. Eaton, Ferns of North America, ii., t. 46. Correvon, Les Fougeres 

 rustiques, p. 138. 



Fi^. 137. Frond of Nephrodium rigidum 

 (i nat. size). 



Under cultivation, N. rigidum is a free-growing species, and the fact of 

 its being found growing wild generally upon chalky soils shows that by its 

 natural habit it is well adapted for planting on artificial rockwork. Correvon, 

 in his excellent work, " Les Fougeres rustiques," states that, although on the 

 Jura Mountains and on the Alps, the leafy parts of the plant are developed 

 in full sun and under the influence of a warm and dry atmosphere, its rhizome 

 (prostrate stem) and roots usually penetrate to a great depth through pebbles 

 and limestone, where they remain in a permanent state of moisture. 



Eaton, in his exhaustive work on " Ferns of North America," mentions 

 (vol. ii., p. 4) two distinct forms of this species, viz., N. r. pallidum of Link, 

 found in the South of Europe, a variety with fronds less sharply toothed and 



