SECT. vm. ASPIDIE^E. 347 



secrete a perfume like new-made hay. From a similar 

 cause, Lastrea rigida was botanicaUy known as Poly- 

 podium fragrans. This coumarine odour is possessed by 

 several other ferns, notably by Cheilanthes odora. 



The Oleandra, which is a foreign genus, has simple 

 fronds articulated near to the rhizome, and its sori are 

 placed on the tips of the parallel veinlets. The Ole- 

 andra neriiformis, which grows on open spots, has an 

 erect rhizome, and assumes quite a shrubby habit, rising 

 to from four to six feet, and bearing at intervals whorls 

 of fronds. 



In the genus Polystichum, the fronds spring in tufts 

 from a short slow-growing caudex. They are rigid, 

 linear or lanceolate, and either pinnate, bipinnate, or 

 tripinnate. The upper terminations of the fronds are 

 sharp and spinous, while the pinnse are auriculate at 

 their base above, and oblique below. Circular sori are 

 seated on the anterior branches of the parallel veins, 

 and these are covered by circular indusia, opening all 

 round and remaining attached by a short central stalk. 

 The free venation and this 

 peculiar form of the sorus 

 and indusium are the dis- 

 tinguishing characters of the 

 genus. Fig. 58 shows a sorus 

 and indusium of Polystichum 

 or Aspidium, which differ 

 only in venation. One of 

 the spinous, serrated pinnse of 



the Holly fern, Polystichum Fig ~ go a^tadnm of 

 Lonchitis, is represented in 



fig. 59 ; it is auriculate at its base above and oblique 

 below, with its sori disposed in regular series on each side 

 the mid-vein; these often become confluent at maturity. 

 This beautiful Alpine fern, which is of a deep glossy green, 

 has linear lanceolate, and simply pinnate fronds. The 



