230 



THE SPORE-PRODUCING ORGANS 



[CH. 



advantage of this is clear, since it provides for the self-nutrition of the 

 sporophyll. Morphologically it has the effect of shunting \\\q. pJiylctic margin, 

 now acting as an indusium, from the actual margin to the lower surface of 

 the pinna (for development of this see below Fig. 237). 



Among the Blechnoid Ferns, however, a further change is seen — the reverse 

 of fusion, viz. the disintegration of the fnsion-sorus. The fusion-sori become in- 

 terrupted, but not necessarily so as to resolve them again into their original 

 constituents. This appears occasionally in Blechmim itself But it has become 

 a constant feature in the sori of Woodivardia and Doodya, where short lengths 



MM [ 



Fig. 228. Drawings illustrating the disintegration of the Blechnoid fusion-sorus (shaded), and its 

 relation to the venation. A=Blechtmm boreale; B, C, D = Blechiium pwictulatum, var. Krebsii; 

 D, drawn on a higher scale; E= Scolopendrium vulgar e { = Phyllitis scolopendriuin). A, B, C, E, 

 slightly enlarged. Z? x 6. 



of the fusion-sorus appear separate from one another, each covered by its 

 own indusial flap. Steps in this remarkable process of disintegration of the 

 fusion-sorus may be seen in BlecJiniun pnnctidatum, Sw. var. Krebsii Kunze, 

 from S. Africa (Figs. 228, 229). Normal specimens of the species have the 

 usual fusion-sorus. But in var. Krebsii the pinnae are relatively broad : the 

 fusion-sori become wavy, and are thrown into strong curves (Fig. 228, B^\ 

 finally they are interrupted in various ways (C, D). The most interesting 

 are those where the isolated portions face one another, giving a disposition 

 corresponding to that seen in Scolopendriuni (Fig. 228, E). It can hardly be 



