and Woody Tissues of Ferns. 327 



that the cells immediately surrounding the fasciculi of the netted 

 cylinder have a light-brown tint. 



Asplenium viride. 

 The petiole has a single central fasciculus, without a dark 

 sheath. 



The rhizome shows no dark tissue in its interior. 



Asplenium Trichomanes. 

 The petiole has a single central fasciculus and a cortical layer 

 of dark substance, much thickened at the base. 



The rhizome has the general parenchyma of a brownish tinge, 

 with a darker tissue (continuous with that of the petioles) form- 

 ing a cortical layer, and also partially ensheathing the vascular 

 bundles. The anastomosis of the fasciculi of the netted cylinder 

 is very close. 



Asplenium Ruta muraria. 



The petiole has a single central fasciculus, containing a double 

 vascular cord, and surrounded near the base with a sheath of 

 dark tissue. 



The rhizome has the same general arrangement as in the last 

 species ; only the dark tissue about the netted cylinder is less 

 marked, and is mainly derived from the sheaths of the petiolar 

 fasciculi. 



Asplenium septentrionale. 



The petiole has a single fasciculus, with a dark sheath at the 

 base. 



The rhizome has also a thin stratum of dark tissue round the 

 fasciculi of the netted cylinder, as in the last species, — especially 

 on their outer side*. 



Woodsia ilvensis. 



The petiole has a single fasciculus, without a dark sheath. 



The rhizome shows no dark tissue in its interior. 



Cystopteris fragilis. 



The petiole has two fasciculi, running into one about the 

 middle of the frond, without dark sheaths. 



The rhizome shows no dark tissue internally, but the outer 

 stratum of the vascular bundles of the netted cylinder has a 

 distinctly fibrous character. 



Adiantum Capillus Veneris. 

 The petiole has a dark glossy cortical layer, and a single fas- 



* In decaying parts of the rhizome, the central parenchyma becomes 

 brown, presenting somewhat the appearance of the dark central tract of 

 Allosorus crispus. 



