74 



THE BIOLOGY OF A PLANT. 



transverse and longitudinal sections, and these should be studied 

 together until their relations are thoroughly mastered. 



The following table gives brief definitions of the leading 

 vegetal tissues as found in Pteris and elsewhere : 



PRINCIPAL ADULT VEGETAL TISSUES. 



These six tissues are not only found in the rhizome, but ex- 

 tend throughout the roots and the fronds as well. Moreover, all 

 the tissues not only of the fern but of all higher plants are va- 

 rieties of them. 



Special Account. It must not be forgotten that the differences 

 between tissues are only the outcome of the differences between 

 their component cells (p. 15). So that the study of the histology 

 of the rhizome, even if preceded (as it may well be) by a dissec- 

 tion, and a naked-eye examination of some of the tissues, eventually 

 resolves itself into the careful microscopic study of the several 

 kinds of cells composing those tissues. 



The mature parts of the rhizome contain at least nine very 

 different kinds of cells, the characteristics and grouping of which 

 are shown in the following table. In the apical buds, however, 

 this arrangement disappears, and all the cells become closely 

 similar. 



