362 



PART IV. CLASSIFICATION. 



along its length, and overlying the sorus (e.g. Asplenium [Fig. 214 

 .E], Blechnum. Scolopendrium [Fig. 217];. In some cases, where 

 the sori are near the margin, they are protected by a false 

 indusium, which is merely the incurved margin of the leaf (e.g. 

 Cheilanthes, Adiantum, some species of Pteris [Fig. 214 C]}. In 

 Pteris aquilina, and some other species, in addition to the false 

 indusium, there is also a membrane along the inner side of the 



FIG 217. Scolopendrium vulgare (Hart's-tongue Fern). A Transverse section of a sorus ; 

 indusinm; * g sporangia. B-E Sporangia ; B and E seen sideways ; C in front ; D from 

 the back ; F a spore. (A x 50 ; B-E x 145 ; F x 510 : after Strasburger.) 



sorus, which is a kind of lateral indusium, adapted to protect a 

 continuous marginal sorus. 



In some forms (e.g. Aspidium Filix-mas, Fig. 215) the stalks of 

 the sporangia bear glandular hairs ; sometimes even the sporangia 

 themselves. 



