IO2 



PLANT LIFE. 



remaining thin-walled, may become greatly thickened in 

 certain regions, or even throughout the cortex. These 



FIG. 115. 



FIG. 116. 



FIG. 115. Prickles on the stem of a rose. Natural size. After Prantl. 



FIG. 116. A longitudinal section through a rose prickle in a young stage, showing how 

 the sub-epidermal (cortical) tissues enter into the structure of the emergence. Magni- 

 fied 200 diam. After Rauter. 



FIG. 117. Transverse section of the stem of Elatine, showing intercellular canals, c. 



Magnified about 15 diam. After Reinke. 



mechanical cells are likely to be aggregated in clusters or 

 strands, and serve an important purpose in strengthening 



