392 



PART III. THE CLASSIFICATION OF PLANTS. 



aquilina, and some other species (section Ornithopteris), in 

 addition to the false indusium, there is also a membrane along the 

 inner side of the sorus, which is a kind of lateral indusium, 

 adapted to protect a continuous marginal sorus. 



In some cases hairs of various form, termed parapliyses, also 

 spring from the placenta among the sporangia ; not uncommonly, 

 when the sorus is naked, these hairs are scaly, often peltate, and 



Fie. 260. Scolopendriitm vulgare (Hart's-tongne Fere). A Transverse section of a soras; 

 indusium ; 8 g sporangia. B-E Sporangia ; B and E seen sideways ; C in front ; 1) from 

 the back ; F a spore. (-4 x 50 ; B-E x 145 ; Fx 540 : after Strasburger.) 



serve to protect the sporangia (e.g. Notochlsena, Platycerinm, Ple- 

 opeltis, Hymenolepis, etc.). In some forms (e.g. Aspidium Filix- 

 mas) the stalks of the sporangia bear glandular hairs ; sometimes 

 even the sporangia themselves (e.g. Polypodium crassifolium) . 

 With the possible exception of the Osmundacese, each sporangium 



