THE LIFE-HISTORY OF A FERN 



[CH. 



and the differentiation of the mesophyll into palisade and spongy parenchyma 

 is not marked (Fig. 8). In these respects they resemble the leaves of Angio- 

 sperms of similar habit. In the roots of Ferns, as in those of Seed-Plants, 



Fig. 8. Transverse section of part of pinnule of Dryopteris ( x 150), showing 

 epidermis, and the spongy mesophyll, with an internal glandular cell. 



Fig. Q. Transverse section of a root of a Fern [PeUaea] ( x 150). Outside lies 

 the sclerotic cortex, limited internally by a definite endodermis. There 

 are two groups of protoxylem ; a very broad pericycle, of 3 or 4 layers, 

 surrounds the vascular tissues. 



there is a superficial piliferous layer, a broad cortex, and a contracted stele. 

 But usually the inner cortex is very strongly lignified, up to the endodermis, 

 which is thin-walled (Fig. 9). The pericycle which follows is variable, some- 

 times being greatly enlarged as a water-storage-tissue. The protoxylems 



