and Woody Tissues of Ferns, 329 



by the thickening of the dark cortical layer continuous with the 

 substance of the rhizome. 



The rhizome is almost wholly composed of dark substance, 

 both externally and internally, the pale tissue forming only thin 

 sheaths round the several fasciculi of the netted cylinder. 



Trichomanes radicans. 



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

 but with a fibrous development in the cambium-coat. 



Hymenophyllum Tunbridgense and Wilsoni. 



The petiole has a central fasciculus, surrounded by a dark 

 cortical fibrous layer, continuous with that on the exterior of the 

 rhizome. 



The rhizome consists of a cortical coat of dark tissue (dense 

 and fibrous internally, loose and chaffy on its outer surface), and 

 of a layer of pale tissue surrounding the cambium-coat of the 

 single central fasciculus or vascular cord. 



Osmunda regalis. 



The petiole has a crescentic fasciculus, with a dark band on 

 its concavity, which looks towards the axis of the rhizome. 

 These structures are imbedded in a pale parenchyma. As the 

 petiole tapers to its connexion with the rhizome, the dark band 

 disappears, and the pale tissue is reduced to a mere sheath, by 

 the thickening of the dark cortical layer. 



The rhizome has a thick layer of dark tissue externally, con- 

 tinuous with the cortex of the petioles, and a thin sheath of pale 

 tissue within, round the vascular cylinder and the fasciculi con- 

 necting it with the petioles. The vascular cylinder is solid, 

 having no obvious reticulations in its walls, from the closeness 

 of the fasciculi, and the absence of any cambium-layer between 

 their inner surface and the cellular tissue of the axis which they 

 enclose. 



Botrychium Lunaria. 



The petiole has two fasciculi, united at the base, without dark 

 sheaths. 



The rhizome has a vascular cylinder with very few openings 

 or reticulations, and with a cambium-layer only on its exterior. 

 There is no dark tissue, except the cuticular investment. 



Ophioglossum vulgatum. 



Stem fistulose, with eight or nine fasciculi in the wall, without 

 dark sheaths. 



In the following Table the species are arranged with reference 

 Ann. % Mag. N. Hist. Ser. 3. Vol. vi. 22 



