392 



PART III. THE CLASSIFICATION OF PLANTS. 



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

 addition to the false indusiura, 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 paraphyses, also 

 spring from the placenta among the sporangia ; not uncommonly, 

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



j 



FIG. 260. Scolopendrium vulgare (Hart's-tongue Fere). A Transverse section of a soius; 

 t indusium ; sg sporangia. B-E Sporangia; E and E seen sideways ; C in front; D from 

 the back ; F a spore. (A x 50 ; B-E x 146 ; Fx 540 : after Strasburger.) 



serve to protect the sporangia (e.g. Notochleena, Platycerium, Pel- 

 tolepis, 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 



