128 WAYSIDE AND WOODLAND FERNS. 



3000 feet. Its world range includes Northern and Western 

 Europe, Siberia, and the Himalaya, and North America. 



The name selaginoides is Latin, and indicates the likeness of 

 the species to some of the Lycopodiums, for which Selago was 

 once the genus name. 



The Quillworts (Isoetes). 



The Quillworts form a genus distinct from Selaginella, but in- 

 cluded with it in the same Natural Order. They are plants of 

 upright habit, without any apparent stem, the leaves all springing 

 direct from a corm which is really a suppressed stem, solid and 

 tuber-like. But even this corm cannot be seen without cutting 

 the plant up, for it is completely wrapped round by the 

 expanded bases of the leaves. It has a depressed upper side, 

 and its continued increase in size is in the direction of thickness 

 rather than height. The leaves are quill-shaped throughout 

 the greater part of their length, but have a greatly dilated 

 triangular base. Attached to the inner surface of the sheathing 

 base, and partly enclosed by it, is the capsule or sporange. The 

 outer series of leaves produce megasporanges ; the inner series 

 microsporanges. Between the whorls of complete leaves there 

 is a whorl of imperfect and barren leaves which are small and 

 without the sheathing base. The megasporange may contain 

 four or more megaspores which are marked on the upper side 

 with three radiating lines along which the spore bursts in 

 germination. The sporanges do not split open to release the 

 spores, which are consequently retained until the tissue of the 

 leaf-base decays. The production of the prothallium within the 

 yet unopened megaspore, and the escape of antherozoids from 

 the microspore follows closely upon what has been described in 

 relation to Selaginella (Plate 143). 



There are two according to some authors, three British 



