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PHARMACEUTICAL BOTANY 
Stems, and roots of secondary growth with open collateral fibro- 
vascular bundles, radially arranged about pith. 
Exogenous stems. 
Medullary rays present. 
Cambium. 
Roots developing secondary structure. 
Flowers tetra- or pentamerous (parts of each whorl, four or five or 
multiple thereof). 
Fig. 129.— Morphology of a typical dicotyledonous plant. A, leaf, pinnately- 
netted veined; B, portion of stem, showing concentric layers of wood; C, ground- 
plan of flower (the parts in s’s) ; D, perspective of flower; E, longitudinal section 
of seed, showing dicotyledonous embryo. (Gager.) 
Sub-class a. — Archichlamyde.e 
Those dicotyledonous plants in which the petals are distinct and 
separate from one another or are entirely wanting. That group of 
