I02 



PLANT LIFE. 



remaining thin-walled, may become greatly thickened in 

 certain regions, or even throughont the cortex. These 



Fk. 



Yic. 



lib. 



Fig, 115, — Prickles on the stem of a rose. Natural size. — After Prantl. 



Fh.. 116. — A longitudinal section through a rose prickle in a young stage, sho\\ing hrjw 

 the suh-epidermal (cortical) tissties enter into the structure of the emergence. Magni- 

 fied 200 diam, — After Ranter, 



l''iG, try, — Transverse section of llie stem of Elatine, showing intercellular canals, 

 Magnified about 15 diani, — After Reinke. 



mechanical cells are likely to be aggregated in clusters or 

 strands, and ser\'e an important purpose in strengthening 



