MOSSES AND FERNS 



CHAP. 



it. The stolons arise from the bases of these leaves, apparently 

 as adventitious buds. They may remain dormant for a long 

 time, as very many more of the very small ones are found than 

 those that are fully developed. These finally bend upward, 

 and the scattered scale-like leaves give place to the perfect 

 green ones. The main rhizome is occupied by a central 

 cylinder composed of a network of anastomosing bundles. 

 Inside of this cylinder is a medulla made up of large parenchyma 



Fig. 162. — A, Vertical longitudinal section of the apex of a rhizome of Adianiiim eviarginatutn 

 (Bory), X25; B, the central part of the same, X 180 ; L, a young leaf; C, cross-section of a 

 similar stem apex, X 180 ; D, apex of a young leaf of Onoclea struthiopteris, showing the apical 

 cell ix). 



cells, and communicating with the cortex by means of the 

 foliar gaps, or spaces between the bundles. 



Fig. 162, A shows a longitudinal section of the apex of a 

 stem oi Adiantum emarginatuni, which shows the typical appear- 

 ance in the Polypodiaceai. The apex of the stem forms a 

 slight cone, whose centre is occupied by the large initial cell, 

 which is deeper than broad. In cross-section it shows much 

 the same form. Divisions occur, evidently, only at compara- 

 tively long intervals, and each segment presumably gives rise to 

 a leaf The first division in each segment is longitudinal and 



