34 Our Native Ferns, 



In Cyrtomium the indusium is the same as in Polvstichum, 

 but the veins tend to unite near the margin. 



Fig. 10. Aspidium {Nephrodium) Fig. 11. Aspidium (Polystichum) 



rigidwm, Swz., vai*. argviuTHi D. C. muniium, Kf. Enlarged section 



B. Enlarged segment showing showing indusia. (Original.) 

 indnsia. (Original.) 



53. Nephrolepis has roundish sori borne at the apex of the 

 upper branch of a free vein, near the margin of the frond. The 

 indusia are usually reniform fixed by the sinus or base and open 

 toward the margins of the pinnae. 



54. Cystopteris.— The bladder-ferns take their popular 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 Aspidium, 

 but are usually more delicate in texture. 



55. 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 margins 

 of the contracted fertile frond being strongly revolute and con- 

 cealing the fruit. O. Struthiopteris has necklace-shaped pinnse, 

 crowded confluent sori, and free and simple veins. O. sensibilis 

 has panicled berry-shaped pinnules and copiously anastomosing 

 veins. 



56. Woodsia (Fig. 12) has round- 

 ish sori borne on the back of the veins 

 with the indusia attached beneath the 

 sporangia and flat and open or early 

 bursting at the top into irregular la- 

 cinise or lobes. In Euwoodsia the in- 

 dusia are flat and open from an early 

 Fig. 12. WbotWa oSfatso, Tori'. . ■i\^ x.\. • to. j -v 1 



T, , , 4. , . , \, Stage with their cleft and ciliate mar- 



Enlarged section of pinnule show- *^ 



ing venation and inferior indusia. gins concealed under the sori. In Hy- 

 (Originai.) POPELTis the indusium is more con- 



spicuous and encloses the sporangium at first but soon bursts at 

 the top forming several jagged lobes. 



