The Maidenhair Spleenwort 



covered by indusia, which open along their length on 

 the side facing the midrib. All the Spleenworts show 

 these linear sori, covered in almost every instance by 

 indusia, so that it is not very difficult to tell when a 

 fern belongs to the genus Asplenium. 



Before we leave the Wall-rue let us recall what we 

 learned in the last chapter about ferns that grew on 

 walls and rocks. They were not, as a rule, tall plants, 

 and their leaves were generally small and of a hard 

 texture. Well, the Wall-rue is a good example of such 

 a fern. Possessing such small, leathery leaves, it loses 

 little of its scanty supplies of water through transpira- 

 tion. Thus we see that the leaves have become small, 

 so that the little Wall-rue may husband every drop of 

 water that may reach its roots. 



Farther along, on the same wall, we are almost 

 certain to meet with another diminutive fern, the 

 Common or Maidenhair Spleenwort. Like the Wall- 

 rue, it has taken advantage of one of the crevices of the 

 wall, into the utmost recesses of which it has pushed its 

 fibrous roots. The contrast between the delicate green 

 fronds and the drab-coloured stones over which they are 

 spread is most pleasing to the eye. These fronds are 

 once pinnate, with pinnae varying in number from seven 

 to twenty pairs, but it is only in exceptionally well- 

 developed specimens that twenty pairs of pinnae are to 

 be found. The tip of the frond bears an odd pinna. 

 The pinnae are all so shortly stalked that they appear 

 stalkless. They are dark green in colour, oval in shape, 

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