274 REPRODUCTION, EVOLUTION, ETC. 



from the size of peas up to several centimetres in diameter in which 

 the cells were arranged like those of a Lithothamnion although the 

 cross walls were not well marked. 



Nematophyceae: Nematophy tales. Figs. 177, 178. 



Two genera are now grouped in this assemblage which has 

 recently been estabhshed by Lang (1937), and although he regards 

 these forms as land plants, nevertheless they have so many features 



Fig. 177. Nematophy tales. Nematothallus. A, specimens on rock ( x f). B, large 

 and small tubes, the former with fine annular thickenings (x 150). C, cuticle 

 (x 150), (After Lang.) 



in common with the algae that it is felt proper to include them here. 

 It is perhaps almost too speculative to suggest that they represent 

 Church's transmigrant form, but it would appear that they must 

 either be regarded as highly developed algae which adopted a land 

 habitat, or else as the most primitive of all true land plants. The two 

 genera agree closely in their morphological structure, and although 

 they are both frequently found associated with each other in the 

 Devonian rocks the two structures have not yet been found in 

 organic connexion. In spite of this it is very probable that the 

 leafy Nematothallus was the photosynthetic lamina of the stem-like 

 Nematophyton and may also have functioned as the reproductive 



