354 CETERA CH. PAKT n. 



exposed situations they are always covered with a glau- 

 cous secretion. The veins diverge from the footstalk 

 at the base of the pinnules, branch out above, and 

 extend to the teeth or serratures, as in fig. 63. The 

 sori, which are produced on the inner side of the veins, 

 are linear, elongated, and eventually become confluent, 

 covering the whole under-surface of each fertile pinnule. 

 The indusium, which is only traceable in the earlier 

 condition of the fructification, is white, and the free 

 inner margin is somewhat jagged. 



Changes as remarkable take place in the sori of the 

 Asplenium lanceolatum. At first, when the sori are 

 covered by their white indusium, they are oblong, but 

 they become circular as they enlarge, and eventually often 

 confluent, so as to form a line round the whole under- 

 margin of the sharply toothed pinnule. This fern, which 

 is indigenous in the Atlantic islands, and is found in the 

 Channel Islands, as well as in the maritime counties of 

 England and Wales, grows in the crevices of rocks and 

 old walls, or clothes the sides of wells and deserted mines. 

 It belongs to the section which has a mid-vein. 



The genus Ceterach apparently belongs to that section 

 of ferns which have a vertical ring, and no indusium ; 

 but its affinities ally it closely with Asplenium. Its 

 want of an indusium is supplied, perhaps occasioned, by 

 the abundance of chaffy scales which cover the back of 

 the fronds. The lateral veins are alternate and irregu- 

 larly branched, with the branches anastomosing towards 

 the margin. The sori are oblong or linear, attached to 

 the upper side of the anterior branches except the last, 

 which is on the opposite side of the lower branch. The 

 British species, Ceterach officinarum, or Scaly Spleen- 

 wort (fig. 64), has deeply pinnatifid, lanceolate fronds, 

 with oblong, obtuse, alternate segments, and linear sori. 

 The whole of the under-surface is densely clothed with 

 brown, pointed, imbricated scales, finely serrated at 



