■jo 



STRENGTHENING DEVICES 



ery either as bands or strands of collenchyma and stereome 

 fibers and these structures are frequently reinforced by addi- 

 tional mechanical tissue in the phloem <>r iu>t outside of it i Fig. 

 45 i. The vascular bundles themselves frequentlj furnish excellent 

 examples of the girder, masses of stereome being found on the 

 outside- of the phloem and on the inside of the xylem flic. 

 45, D). The resistance of these tissues to cutting and breaking 



Fie ction of stems showing arrangement of strengthening 



: ./, burdock with strands of collenchyma a/, .it periphei 



cular bundles. />'. sw r, showing a similar arrangement. C, moon- 



bowing cylinder • outside "t vascular bui 



li with strand ome fibers at periphery of stem ami a! 



inner and outer sides <>t" tin- bund! cular bundles; me. 



affords abundanl evidence of their hardness and rigidity. It 



ma) be surprising to note thai the sustaining strength of the 



me fibers is equal to that of the best wrought iron 01 



