270 



CORDAITEAE 



[CH. 



spermatozoids were developed. The microspores shown in fig. 

 482, B, have a maximum length of 0-1 mm. : Kenault describes 

 some as 0-9 mm. long while others are much smaller. Fig. 481, F, 

 is a transverse section of a staminate inflorescence showing near 

 the centre five groups of microsporangia, each sporangium having 

 the form of a curved incomplete dark band indicating that de- 

 hiscence has occurred. 



FIG. 482. Cordaianihus. Microsporangia, A, and Microspores, B. 

 (University College Collection, London.) 



Mesoxylon. Scott and Maslen. 



This generic name was instituted for stems obtained by 

 Messrs Lomax from the Lower Coal Measures of Lancashire 1 

 previously referred by Scott 2 to Cordaites and Poroxylon. Further 

 investigation showed that while agreeing closely with those 

 genera they possessed certain distinctive features demanding 

 recognition. The name chosen suggests the intermediate nature 

 of the stems. The more striking features may be summarised 

 as follows: In the largest specimens so far described the stem, 



1 Scott and Maslen (10); Scott (12). 



2 Scott (09) B. pp. 511, 526. 



