DEFINITIONS OF TERMS. 



than an inch or two above ground. When a stem rises to 

 a height of many feet -above the ground it forms a trunk, 

 becomes tree-like, and ferns of this habit are called tree- 

 ferns. The elongation of a stem to form a trunk is a 



process accomplished by the heightening of the crown 

 of the cormus by the retention, each year, of the bases 

 of the fronds which rise above it in a circlet. The older 

 the fern, therefore, the higher, up to a certain limit, will 



