LAURENTIAN AND EARLY PALAEOZOIC. 



23 



have more recently named it, Nematophyton, as a prime- 

 val gymnosperm allied to those trees which Unger had 

 described from the Erian of Thuringia, under the name 

 Aporoxylon* Later examples of more lax tissues from 

 branches or young stems, and the elaborate examinations 

 kindly undertaken for me by Professor Penhallow and 



Fig. 4. — Nematophyton Logani (magnified). Restoration, f 



referred to in a note to this chapter, have induced me to 

 modify this view, and to hold that the tissues of these 

 singular trees, which seem to have existed from the be- 



* " Palacontologie des Thuringer Waldes," 1856. 

 t Figs. 2, 3, and 4 are drawn from nature by Prof. Penhallow, of 

 McGill College. 



