56 ELEMENTARY BIOLOGY. [CHAP. 



will be observed that the internodes do not become crowded 

 towards the free end, and there is nothing comparable to 

 the terminal bud of Chara with its numerous rudimentary 

 appendages. 



When the fronds have attained their full size, the edges 

 of the pinnules will be observed to be turned in towards 

 the underside, and to be fringed with numerous hair-like 

 processes which roof over the groove, enclosed by the 

 incurved edge. At the bottom of the groove, brown 

 granular bodies are aggregated, so as to form a streak 

 along each side of the pinnule. The granules are the 

 sporangia, and the streaks formed by their aggregation, 

 the sori. 



Examined with a magnifying glass, each sporangium is 

 seen to be pouch-shaped, like two watch-glasses united by 

 a thick rim. When ripe, it has a brown colour, readily 

 bursts, and gives exit to a number of minute bodies which 

 are the spores. 



The plant now described is made up of a multitude of 

 cells, having the same morphological value as those of 

 Chara, and each consisting of a protoplasmic mass, a 

 nucleus and a cellulose wall. These cells, however, become 

 very much modified in form and structure in different 

 regions of the body of the plant, and give rise to groups of 

 structures called tissues, in each of which the cells have 

 undergone special modifications. These tissues are, to a 

 certain extent, recognizable by the naked eye. Thus, a 

 transverse section of the rhizome shews a circumferential 

 zone of the same dark-brown colour as the external epi- 

 dermis, enclosing a white ground-substance, interrupted by 

 variously disposed bands, patches, and dots, some of which 

 are of the same dark-brown hue as the external zone, while 

 others are of a pale yellowish-brown. 



