114 



PLANTS, THE FOOD OF ANIMALS 



mental cells, all firmly attached, and forming a tough and re- 

 sisting framework or skeleton, giving strength and rigidity 

 to the whole. These woody masses are together called the 

 stereome. Finally there are smaller and more or less circular 

 patches of cells with thick cellulose walls, which form the most 

 important organs of the rhizome, the aggregates being termed 

 vascular bundles. 



If we examine a vertical or horizontal section of the rhizome 

 (Fig. 45) we find that these internal masses of stereome and the 

 vascular bundles are composed of elongate woody and cellular 

 structures, firmly attached end to end so that continuous sup- 



FIG. 45. Longitudinal section of a vascular bundle showing the conducting 

 system of the plant in lengthwise section. (From Sedgwick and Wilson.) 



porting structures and tubes traverse the rhizome from end to 

 end, the former serving as an internal skeleton, the latter as 

 conducting and feeding organs. 



In the immediate vicinity of the growing tip of the rhizome 

 the cells, with the exception of the apical cell, are practically all 

 alike and of the fundamental parenchyma type forming the 

 primary meristems, but they become differentiated at a short 

 distance from the apical cell to form cells of varying structure 

 and function, some becoming vascular cells, while others are 

 transformed into lifeless stereome. 



These various groups of cells, tubes, supporting structures, 

 etc., are not only continuous throughout the main trunk of the 

 rhizome but are also continuous, through branches, in every 



