XLiv] WOODWARDIA AND DOODIA 183 



by the sori of Woodzvardia being sunk in the mesophyll, while those of 

 Doodia are superficial. The primary veins are linked together by the com- 

 missures that bear the sori: the veins passing out from these may be free, 

 as in D. media (Fig. 704, D\ or reticulate with wide meshes, as in W. radicans 

 (Fig. 704, y^) and arcolata. The leaves are usually homophyllous, but some- 

 times dimorphic, as in W. areolata. 



The hypothesis that these Ferns represent a Blechnoid type in which the 

 coenosorus has been disintegrated is supported primarily on general grounds 

 of habit, and of the arrangement and structure of the sori. Secondly by the 



Fig. 704 



venation 

 and sori. 



4,B= Woochvardia radicans (L. ) Sw. A -- secondary pinnules. B = part of one pinnule with 

 and sori. C, D=. Doodia media R. Br. C= primary pinna. /? = part of a pmna with venation 

 (After Diels, from Nadir l. Pflanzcnfam.) 



fact that they show the Blechnoid anatomy, with leaf-traces springing from 

 the sides of the leaf gaps, as two strands, one or both of which soon abstrict 

 smaller strands, the number of these varying roughly according to the size 

 of the petiole (Studies IV, p. 403, Figs- iS> 16). The hypothesis is also sup- 

 ported by the details of development of the fertile pinnae, which correspond 

 closely to those seen in Eu-Blechmim. The lateral pseudo-wing of the fertile 

 pinna arises by segmentation directly from the marginal series, as in 

 B. brasiliense (Fig. 692, 12, a-e). It attains considerable size before any sign 

 of the sorus appears: and when it does the similarity between W. radicans 



