THE ANGIOSPERMAE : STEMS 



887 



Outer phloem 



Xylem 



Inner phloem 



Fig. 873. — Atropa belladonna. Transverse section of 

 steni showing groups of phloem elements at the 

 margin of the pith. 



Fig. 874. — Tecoma radicans. Transverse section of the stem 

 showing anomalous cambium inside the protoxylems, pro- 

 ducing conspicuous wedges of medullary phloem. 



only in certain families [e.g., Cucurbitaceae and Solanaceae), sometimes in 

 members with all types of growth, sometimes only in climbing species of 

 the family. 



The second type is the centric bundle (Fig. 875). This is usually, though 

 not invariably, a closed bundle and is commoner in ]Monocotyledons, especially 

 in the underground stems, than in Dicotyledons. It may have the xylem 

 in the centre and the phloem outside in which case it is called peri- 

 phloic or amphiphloic, or else the reverse when it becomes perixylic 

 or amphixylic. 



