174 



PART II. THE INTIMATE STRUCTURE OF PLANTS. 



[ 33. 



In the collateral bundle, the wood and the bast are so situated 

 that they both lie on a straight radial line drawn through the 

 bundle from the centre of the member to the surface, the wood 

 being nearer the centre, and the bast nearer the surface (see 

 Fig. 130). This type of bundle is common in the monostelic or 



FIG. 133. Transverse section of an open, collateral, conjoint, vascular bundle of the 

 stem of Ranunculus repens: s spiral vessel of the protoxylem at the inner (central) end of 

 the wood ; m pitted vessel of the wood ; c cambium ; v si bieve-tube of the bast with 

 adjacent granular companion-cells; vg sheath of sclerenchymatous conjunctive tissue. 

 (After Strasburger : x 180.) 



schizostelic stems and leaf-stalks of Phanerogams and of some 

 Pteridophyta (Osmundaceae, Ophioglosseoe, Equisetum). 



In some stems (e.g. Myrtacese, Onagracese, Apocynacea?, Solan- 

 acese, most Convolvulacese, Cucurbitacese, etc.) there is a second 



