GREEN-RIBBED SPLEENWORT. 39 



their separation as distinct species, but against the suggestion 

 that viride may owe its differences to its more alpine habit, it 

 may be pointed out that though viride has been found at an 

 elevation some 800 feet greater than trichomanes, they may also 

 frequently be found at the same level. They may, indeed, be 

 found growing on the same mass of rocks, and in that case 

 trichomanes will most probably be found in a higher, drier 

 position, whilst viride occupies crevices near the base where 

 moisture is abundant. (Plates 33, 44.) 



On a superficial glance the two plants are exactly alike, but 

 considered more intimately the Green-ribbed Spleenwort will 

 be found to carry its fronds more horizontally. A. trichomanes 

 bears its upper fronds erectly against the rock with a lateral 

 curve, and its lower ones with a downward curve. A. viride 

 affects curves much less, and its smaller fronds are of a paler 

 green. The most obvious distinction, however, is to be found 

 in the rachis. The stipes may be brown or purple as in 

 trichomanes, but the rachis is as green as are the pinnae, more 

 slender, not keeled, and less broadly grooved. The pinnae are 

 more regularly oval, the teeth more rounded, and the footstalks 

 more developed. The fruit clusters are similar to those of 

 trichomanes, but the indusium appears to be less lasting, and 

 the veins do not fork (if at all) before they reach the sori. It is 

 in fruit from June to September. (Plate 39.) 



The Green-ribbed Spleenwort will not as a rule be found 

 upon walls, but in the crevices of mountain rocks that are pretty 

 continuously moistened. It is a northern fern, and its range in 

 this country is from Shetland southward to South Wales and 

 Derbyshire. It also occurs in the West of Ireland. Beyond 

 our borders, it is distributed over Arctic Europe, the Alps and 

 Pyrenees, North and West Asia, and North America. 



Our forefathers appear to have considered it as identical with 

 A . trichomanes, for it has no folk-name. The English name we 

 have adopted is that used by Withering. Most modern authors 



