PHYLLODES AND CLADODES 



195 



recently proposed by Arber (19 18) and supported by a mass 

 of anatomical evidence, that the leaf of the monocotyledons 

 is in all cases a phyllode, corresponding not to the leaf 

 blade but to the petiole of the dicotyledon leaf. This view 

 is adversely criticised by Goebel. 



Fig. 21. — Cladodes of butcher's Fig. 22. — Acacia nereifolia with com- 

 broom {Ruscus aculeatus). pound leaf, phyllode, and transition 

 Nat. size. form. 3 nat, size. 



What advantage the plant secures by replacing a leaf by 

 a leaf-like stem or petiole it is difficult to see ; unless we 

 assume that the leaf, presumably present in some distant 

 ancestor, was of mesophytic type, and that its disappearance, 



