1865.] EATON — GENUS WOODSIA. 89 



ON THE GENUS WOODSIA. 



By Daniel C. Eaton, M.A. 

 Professor of Botany in Yale College, New Haven. 



This genus of ferns was established by the learned Robert 

 Brown in 1812, for the two species Woodsia Ilvensis and 

 W. hyperborea; afterwards he added a third, W. glabella. These 

 species all have a minute pateriform involucre, covered by the 

 sporangia, and divided into numerous elongated cilise. The 

 genus has since been extended so as to include species having 

 a more manifest involucre, at first globose or irregularly hemis- 

 pherical, the margin commonly ciliated or irregularly laciniated. 

 The genus thus extended embraces twelve or fifteen species, several 

 of them occurring in the north-temperate and sub-arctic zones, and 

 others following the Cordilleras and the Andes, from Mexico to 

 Chile, or inhabiting the mountains of Northern India. All the 

 species are small ferns, growing in tufts, mostly in crevices of ex- 

 posed rocks, the stipes commonly very brittle, and remaining 

 after the fronds have fallen away. 



The species of this genus I propose to arrange as follows : 

 § 1. Stipes articulated, the withered fronds falling away at the 

 joint. Involucre beneath the sorus, pateriform, deeply divided 

 into elongated ciliae which are inflexed over the sporangia.— 

 W. alpina and Ilvensis. 



§ 2. Stipes not articulated. 



A. Involucre as in § 1, but smaller, the ciliae scarcely 



visible among the sporangia. — W. Oregana, scopu. 

 Una, and Mexicana. 



B. Involucre cyathiform or globose, enveloping the 



sporangia, afterwards lacinately cleft into irregular 

 lobes. (Physematium, Kaulf.) — W. incisa, obtusa, 

 mollis, Guatemalensis, Peruviana, Cuming iana, 

 and elongata* 



C. Indusium irregularly sub-globose, cystiform, divided 



into 4-6 ciliated lobes, which are imbricated over 

 the sporangia. — W. pohjsticlioides. 



* W. Caucasica probably belongs here, but I have not had an oppor- 

 tunity of examining it. Hypodcrris Brownii Wallich, also almost un- 

 known to me, is referred to this genus by Mettenius :— it would consti- 

 tute a third section, characterized by reticulated venation. 



