reproduction; evolution 307 



a cuticle; (c) the presence of cuticularized spores; {d) the large size 

 of stem. 



The answer to the last problem has already been suggested (see 

 above) but cuticles in the Codiaceae have not been recorded, al- 

 though the present author has been able to detect a structure some- 

 thing like a cuticle in Halimeda; nor have any species been re- 

 ported that possess two distinct sizes of tubes, although gradations 

 in size occur in both Udotea and Halimeda. In this connexion it 

 may be of interest to refer to Tilden's unsupported suggestion that 

 the land plants arose from forms such as Codium and Caulerpa. It 

 must be admitted that there are no Uving members of the Codi- 

 aceae with stems that approach anywhere near the size of those of 

 Nematophyton. This, however, is not an insuperable objection as 

 the Nematophytales may bear the same relation to the hving Codi- 

 aceae that the fossil Lepidodendrons bear to the living Lycopo- 

 diales. For the present, however, the problem must be left in the 

 hope that further evidence will accumulate. 



REFERENCES 



Spongiostromata 



Fenton, C. L. (1943). Amer. Mid. Nat., 30. 



General 



Johnson, J. H. (195 1). Manual of Phycology, 193-201. Chron. Bot., 

 Waltham, Mass. 



Nematophyceae 



Pia, J. (1927). In Hirmer's Handb. Palaeohot., Munchen and Berlin. 

 Lang, W. H. (1937). Philos. Trans. Roy. Soc. B., 227, 245. 



Reproduction and Evolution 



In so far as the green algae or Chlorophyceae represent the main 

 line of evolution from which it is believed land plants ultimately 

 evolved, it is convenient to consider evolution within that group 

 first. In the past there have been two major views about the origin 

 of the group. According to one, the Chlamydomonadaceae are 

 regarded as the primitive group whereas according to the other the 

 Palmellaceae are. These two views are represented respectively by 

 schemes A and B. Of the two there would appear to be rather more 



