82 



ORIGIN OF CORMOPHYTA 



[CH. 



because this particular type of leaf appears to be much more 

 common than SpJienopteris in the older rocks. Sphenopterids 

 however do occur there, and they appear to have been derived 

 from Procormophytes by the division of the ends of flattened 

 branch systems into more rounded and broader segments. 



Fig. 45. Splienopteris affinis, 

 L. & H., from the Lower 

 Carboniferous of Scotland, 

 showing thalloid foHage. 

 (Reduced |nat.size.) Speci- 

 men No. 667, Carbonifer- 

 ous Plant Coll., Sedgwick 

 Museum, Cambridge. (W. 

 Tams jjhoto.) 



Fig. 46. Splienopteris bifida, L. & H., 

 from the Lower Carboniferous of Scot- 

 land, showing thalloid foliage ( x f ). 

 Specimen V. 162, British Mus. (Nat. 

 Hist.). 



We know very little of the fnictifications associated with 

 either of these types of fronds in Devonian rocks. If Nathorst 

 is right in attributing to Sphenopteridium-like fronds the tufted 

 sporangia of CephaJopteris (Fig. 3G, p. 63), then here at any rate 



