i82 BLECHNOID FERNS [CH 



The vascular connections of the coenosorus arise from two sources. The first is the primary 

 venation of the Matteuccioid type, where each separate sorus springs from the original vein 

 with its long conducting tracheides, extended as shorter storage tracheides into the 

 receptacle. The second consists chiefly of these shorter, almost brick-shaped tracheides 

 characteristic of the receptacle. They link up the veins by commissural loops, and may 

 sometimes be seen to take a course of their own independently of the longer conducting 

 tracheides (Fig. 701, 2of, 21). The relation of the two vascular constituents is suggested 

 by the diagram Fig. 695. Taking the instance of soral disintegration seen in B. spicaut 

 (Fig. 701, 23), in which species it is not an infrequent condition, each soral fragment is 

 covered by its own indusial flap, which is a portion of the phyletic leaf-margin. Frequently 

 a vascular process projecting on the anadromic side represents a part of the derivative 

 commissure. These details, combined with the varying length of the fragments, show that 

 the disintegration of the coenosorus is not a mere resolution into the original sori, but a 

 breaking up of it into arbitrary parts. 



Fig. 703. Transverse section of the stock of Blechnum 

 pmutulatum Sw. var. Kj-ebsii Kze. , showing a structure 

 normal for Blechnum. ( x 3.) Compare Fig. 689. 



WOODWARDIA AND DOODIA 



Such disintegration of the coenosorus as appears sporadically in many 

 species of Blechmnn is stereotyped in Woodwardia and Doodia, becoming 

 in them generic characters. These genera may be held as derivatives from 

 the Blechnum-iyp&, distinguished by a regular partition of the coenosorus 

 into isolated parts, each of which corresponds as a rule to a single loop of 

 the commissure (Fig. 704). Both genera consist of terrestrial Ferns, usually 

 with an upright paleaceous axis; but occasionally it is creeping, as in 

 W. areolata (L.) Moore. The foliage is usually stiff and cartilaginous, 

 especially in Doodia: but in Woodwardia, in accordance with its shady 

 habitat, the leaves are more herbaceous. The two genera are distinguished 



