538 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



ral vary much as regards the dimensions of tlieir caudex, 

 according to favourable or unfavourable circumstances. The 

 rhizoma of Gibotium Barometz is covered with long tawny 

 hair, a circurastance which gave rise to the fable of the 

 Scythian lamb, half animal, half vegetable. It was said to 

 perish, if not already the prey of wolves and other carnivorous 

 animals, after it had consumed all the food within the small 

 semicircle of which alone it had the range, being always united 

 to the parent. The species belong principally to the tropics 

 and southern isles. Thyrsopteris is confined to Juan Fer- 

 nandez. The fibrous coat of the trunk in Dicksonia antarctica 

 is sliced by the New Zealanders and used in constructing 

 houses. 



12. Davalliace^, Gaud. 



Sori inframarginal, globose, or linear, seated at the tip of a 

 vein or veinlet ; indusium lateral, semiorbicular, oblong or 

 linear, persistent, scarious, the upper margin free. 



611. The resemblance of Davalliacew to the Gystopteris 

 section of Aspleniacew is confessedly very close, and without 

 attention to the nervation they are not easy to distinguish. 

 In this tribe, however, the indusium is more constantly seated 

 at the tip of a vein or veinlet ; whereas in the ferns just men- 

 tioned it is situated in the middle. In Davalliacece, moreover, 

 the indusium is adnate through a considerable part of its cir- 

 cumference, and is persistent. From Dicksoniacew they differ 

 in the want of an accessory indusium. Microlepia, Saccoloma, 

 and Bavallia, all agree in this respect. Leucostegia has the 

 sori seated in the sinus of the lacinise, with a scarious indusium. 

 One species seems at first sight to differ from other ferns except 

 PolypocUum anomalum, and certain Acrostichacece, in having 

 the sori on the upper surface ; but the fact is, that this is paler, 

 and looks hke the under surface, because the margin of each 

 joinnule curves upwards. Microlepia differs from this princi- 

 pally in habit. Humata has a coriaceous indusium, and vein- 

 lets thickened upwards. Davallia is known by its tubular 

 indusium, and Saccoloma has a small linear special indusium, 

 with a spurious indusium formed by the reflected margin, and 

 thus passes mio Dichsoniaceoe. The genera just enumerated 



