VIl] 



NEMATOPHYCUS. 



199 



The main distinguishing features of this British species are 

 (i) the absence of two distinct and well-defined forms of tubular 

 elements. The main part of the stem consists of thick walled 



Fig. 40. Nematophycus Stoiriei Barb. Longitudinal section, from a 

 photograph by Mr C. A. Barber, x 45. 



tubes similar to those of N. Logani, but the spaces between 

 them are occupied by thinner- walled and smaller tubes varying 

 considerably in diameter ; (ii) the form of the spaces which are 

 not radially elongated as in N. Logani. 



Fig. 40 shows the undulating course of the tubes as seen in 

 a longitudinal section ; the black colour of some of the elements 

 is due to the fact that the surface of the wall is seen, while in 

 the lighter-coloured portions of the tubes the wall has been cut 

 through. The lighter patch about the middle of the figure 

 shows the form of one of the spaces in which the tubes are 

 freely branched. 



In addition to the two species already described six others 

 have been recorded, but with these we need not concern 

 ourselves in detail. One of these species, N. Hicksi, was found 

 by Dr Hicks ^ in the Denbighshire grits quarry of Pen-y-Glog 

 near Corwen in North Wales. The position of these beds has 



1 Hicks (81) p. 490. 



