CRYPTOGAMS 



403 



produces a transverse rupture of the capsule between the broad cells 

 at its extremity (Fig. 334, E). It then returns suddenly to its original 

 position, only once more to uncoil until it assumes a nearly vertical 

 position. 



The form and insertion of the sori, the shape of the indusium 

 when present, or its absence, all constitute important criteria for 



Fig. 334.— Scolopendrivm tmlgare. A, Part of a section through the fertile portion of a leaf; i, 

 indusium ; eg, sporangia. B-1S, sporangia, in lateral (B, E), dorsal (A), and ventral (C) view ; 

 F, a spore. (A x 50; B-M x 145 ; F x 540.) 



distinguishing the different genera. The sori of Scolopendrium (Fig. 

 333) are linear, and covered with a lip -shaped indusium con- 

 sisting of one cell-layer. They are so disposed in pairs, on different 

 sides of every two successive nerves, that they appear to have a 

 double indusium opening in the middle (Fig. 334, A). In structure 

 the indusium resembles the epidermis, but the stomata are absent, and 

 the chromatophores are colourless. In the genus Aspidium, on the 

 other hand, each sorus is orbicular in form and covered by a peltate 

 or reniform indusium attached to the apex of the placenta. The sori 



