xxxm] 



CORDAITES 



263 



of small rootlets is composed of two zones, an outer parenchyma 

 without cell-contents and an inner parenchymatous tissue charac- 

 terised by the occurrence in some of the cells of tangled masses 

 of fungal hyphae almost always unseptate. In some cases the 

 hyphae bear terminal vesicles similar to those observed on fungal 

 hyphae in the cortex of Podocarpus roots. Osborne makes out 

 a good case for regarding the fungus as symbiotically related to 

 the tissues of the lateral roots, a relationship identical with that 

 in many existing trees, particularly Myrica and Alnus. It is 

 suggested that the formation of the coralline root-tubercles is a 

 feature consistent with the view that Cordaites lived in saline 

 marshes, a physiologically dry habitat favourable to the occurrence 

 of mycorhiza. 



FIG. 478. Root (Cordaitest) exposed in the bed of the Vaal river. 

 (After Mellor and Leslie.) 



Reference has already been made to the habit of Cordaitean 

 roots in the general account of the genus (figs. 468, A, 478). The 

 specimen shown in fig. 478 may be a root of Cordaites (Noegger- 

 aihiopsis} Hislopi, but nothing is known as to its structure 1 . 



1 Mellor and Leslie (06) B. 



