FRUCTIFICATION IN FERNS. 



17 



Fig. 



- H 'oodsia obtusa 



name from the delicate, hood-like indusium which is attached 

 by its broad base on the inner side of the roundish sorus and 

 partly under it. Later this is thrown back and withers away. 

 The veins are free, and the fronds have the aspect of species of 

 Dryopttris, but are usually more delicate in texture. 



51. Onoclea. — This genus contains two quite dissimilar 

 species, which until recently have been separated into two 

 genera by American botanists. Both have dimorphous fronds, 

 the margin of tiie contracted fertile frond being strongly revo- 

 lute, and concealing the fruit. O. strtithioptcris has necklace- 

 shaped pinnse, crowded confluent sori, and free and simple 

 veins. O. sensibz'h's has panicled berry-shaped pinnules and co- 

 piously anastomosing veins. 



52. Woodsia (Fig. 9) has round- 

 ish sori borne on the back of the 

 veins, with the indusia attached be- 

 neatli the sporangia and flat and open, 

 or early bursting at the top into ir- 

 regular laciniae or lobes. In § Eu- 

 woODSlAthe indusia are flat and open 



from an early stage, with their cleft pinnule, showing venation and 

 and ciliate margins concealed under inferior indusia. 

 the sori. In § Hypopeltis the indusium is more conspicuous 

 and encloses the sporangium at first, but soon bursts at the top, 

 forming several jagged lobes. 



53. Dicksonia. — In this genus the small globular sorus is 

 borne in an elevated, globular receptacle, and enclosed in an in- 

 ferior, membranous, cup-shaped indusium. The veins are al- 

 ways free. 



54-. Trichomanes (Fig. 10) has 

 sessile sporangia borne on a filiform 

 receptacle at the summit of a vein. 

 The indusia are tubular or funnel- 

 shaped, with an expanded and often 

 somewhat two-lipped mouth. 



55. Lygrodium.^In our species 

 of climbing-fern the fructification is 

 borne on contracted, forked pinnules showing niethod of Iructiiica- 



..u . • r 1 lion. 



occupymg the upper portion of the 



frond. The ovoid sporangia are solitary or occasionally in 

 3 



Torr. Enlarged section of 



Fig. 10. — Triclionianes radi- 

 ans Swz. Enlarged section. 



