348 



CYSTOPTERIDE^E. 



PART II. 



pinnse are short, arranged alternately and obliquely on 

 the rachis, and extend nearly to its base, which is rather 

 densely clothed with reddish-brown chaffy scales. The 

 other British ferns of this genus 

 are bipinnate. P. aculeatum is 

 rigid, but P. angulare is lax, and 

 drooping. One of its varieties, 

 named proliferum, is abundantly 

 viviparous, producing small bul- 

 bils about the bases of the lower 

 pinnae and pinnules, which readily 

 reproduce the plant. 



All the preceding genera, from 

 Lastrea inclusive, belong to the 

 Aspidiese, an enormous tribe, 

 abounding in species, and almost 

 Fig. 59. pinna of Poiystichum conterminous with the old genus 



Lonchltis. 



Aspidium. 



The Nephrolepis tuberosa and other species bear sub- 

 translucent tubers on the rhizome. They are subter- 

 ranean, ovoid, an inch and a half long, and filled with 

 a nearly translucent mucus. The tubers have a circle of 

 vascular bundles forming a sort of balloon, proceeding 

 from a common base below, and converging to the apex. 9 



Most of the species are tropical, but Lastrea and 

 Poiystichum include several European species, some of 

 which are extremely variable. 



The Onoclea is a remarkable genus from the pinnse 

 being contracted into berry-like globes. Onoclea sensi- 

 bilis is a handsome free-growing American species and 

 appears to have been named sensibilis, from the particu- 

 larly rapid withering of the fronds after being gathered. 



The genus Cystopteris, which has species in both hemi- 

 spheres, is the type of the Cystopteridese, a small group 

 which approaches Aspidiese through Nephrolepis and 



9 Berkeley's ' Cryptogamic Botany.' 



