542 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



inferior point. It is therefore only on a superficial view 

 similar to the indusium of Cyathea. The sori are, in fact, like 

 those of the next tribe, but the insertion of the indusium is 

 different. Acrophorus is a Cystopteris with apical sori. The 

 genus is founded on a Java species. Onoclea is remarkable 

 for the pinnjB being contracted into berry-like globes. 

 There is some difficulty about the nature of the indusium, 

 as the pinnules are so hard and coriaceous as to mask the 

 structure. Ragioptei'is is the same genus with Onoclea. 

 0. sensibilis is a well-known American species, the fronds 

 of which were formerly supposed to die if a single pinnule 

 were squeezed ; but this does not appear to be confirmed by 

 modern observation. 



14. AsPiDiACE^, Presl. 



Sori globose or more rarely oval, seated on the middle of a 

 vein or veinlet, rarely apical ; indusium superior, orbicular, 

 and peltate, or reniform, or ovali-elliptic, fixed to a central or 

 slightly lateral point, or by a longitudinal crest, but free all 

 round ; rhizoma creeping or sub-globose. 



618. This is an enormous tribe, abounding in species, form- 

 ing the old genus Aspidium, and divisible into two distinct 

 sections, one of which contains the immediate allies of Nephro- 

 dium, the other those of Aspidium, Lastrea, Oleandra. 

 Nephrolepis, and Nephrodium, which all belong to the first 

 section, and differ principally in the details of the nervation. 

 Lastrea, for instance, is distinguished from Nephrodium by 

 the veins remaining distinct, while in Nephrodium they 

 inosculate. In Nephrolepis the sori are seated at the tips of 

 the lower exterior veinlets, a character which, however, occurs 

 in some species oi Nephrodium, of a very different habit, and 

 not having the petioles articulated with the rachis, like true 

 species of Nephrolepis. Oleandra has the tips of the parallel 

 veinlets curved upwards, and forming a slightly thickened 

 margin, and is distinguished, moreover, by its simple fronds, 

 which are articulated close to the rhizoma. Nephrolepis 

 tuberosa is singular for the tubers on the rhizoma. These are 

 1 ^-inch long, ovoid, subterraneous, subtranslucid, filled -with a 

 firm mucous subtranslucent substance. They have a circle of 



