CLA OSSIFICATION. 



easily distinguished from the arboreous monocotyledons by the relatively 

 copious branching of the stem. Anatomically the stem is generally well 

 distinguished from the woody tissue uniting outside the pith into a solid 

 cylinder enclosed by a distinct cylinder of bark. In between the two is a 

 very thin tissue (the cambium i which continually adds more wood to the 

 cylinder. The flowers when not reduced usually have their several parts 

 (calyx, petals, etc.) in 2's, 4's or 5's, but 3's are common among the 

 Kanales, and in a few other families. 



Some leaves with palmate venation have the primary nerves more or 

 less parallel and the secondary nerves more or less at right angles to 

 these, e.g., some Zizyphus, some Grewia, some Laurels, etc. The 

 absence of a sheathing base to the petiole and the tertiary venation is 

 however distinctive in these cases. 



Sub-class I — Choripetalffl (Dialy petals© or Polypetalse) 

 (p. 57). 



Perianth leaves, when present, free from one another (not 

 appearing aslobea of a tube), or only those of the calyx united. 

 Stamens free from the corolla (see exceptions below) often 

 m-iny. Carpels rarely two, often one or more than two, free 

 or united. Ovules usually with 2 integuments and a large 

 nucellus. 



The perianth in the Choripetal® is very various. It may 

 be of many spirally arranged leaves (cp. water-lily) i.e., 

 acyclic, or cyclic with 1, 2, or more whor 1 ^, one or more of 

 w hich may be petaloid. In many cases the perianth is much 

 reduced, e,a\, Urticacese, or obsolete, e.g., Piper, Salix. 

 White or brilliantly coloured bracts sometimes replace it 

 functionally but usually surround an inflorescence not a flower, 

 e.g., Houttynia, Poinsettia. A gamophyllous perianth is not 

 to be confused with a growth of a zone of the torus or recep- 

 tacle around. and above the ovary, termed a hypanthium, and 

 '.n which may be placed sepals, petals and stamens (op. a 

 Rose, Pomegranate, or Woodlordia). 



Exceptions : — 



Petals sometimes united at their base or to the staminal tube in Mal- 

 vaceae, Meliaoeae, Ternstoe miaceaa, Polygala, and Leea. Corolla gamo- 

 petalous in the male flower only of some Papayaceae, in both sexes in many 



50 



