7^ 



lit 



76 



THE GEOLOGICAL HISTORY OF PLANTS. 



f 



various heights on the stem, and which form a series of 

 stays like the cordage of a ship. This method of support 



FiQ. 2Q.—Me(falopteri8 Dawsoni, Ilartt (Erian, New Brunswick), rt, Frag- 

 ment of pinna, h, Point of pinnule, c, Venation. (Tlie midrib is not 

 accurately given in this figure.) 



still continues in the modern tree-ferns of the tropics 

 and the southern hemisphere. In one kind of tree-fern 



