TISSUE SYSTEMS ;ir,;j 



meiismatic powers. This constitutes the cambium of the bundle 

 (fig. 738, c). Its cells are usually elongated parenchyma with 

 thin walls and granular protoplasm. By this merismatic layer 

 the bast on the one side and the wood on the other are increased, 

 so that the conjoint bundle grows both inwards and outwards. 

 This fascicii.lar cambium is a primary meristem. 



Fir4. 7.S9. 



Fiij. 739. Collateral bundle from stem of a Monocotylerloii. ph. Phloem. 

 X, Xylem vessels, ^.j;. Protoxylem. p.p/t. Protophloem. Ihe bundle is 

 surrounded by a small celled sheath of sclerenchyma. After Kny. 



The collateral bundle of the second type is similarly de- 

 veloped from the procambium strand. The protoxylem is an 

 annular or spiral vessel of some size, occupying a position in 

 the front of the bundle. Frequently it abuts on a lysigenous 

 intercellular space, as seen in fig. 7.90. The protophloem, again, 



VOL. I. A A 



