160 SYSTEM OF DECANDOLLE. 



23. We may now describe more particularly the es- 

 sential characters of the various divisions given in the 

 table, under the least general of which we shall arrange 

 the different natural families, or collected groups, of the 

 members of the vegetable kingdom, and give their cha- 

 racteristic signs, etc. 



24. This last subject has been treated by us thus : 

 We have selected those natural families which yield a 

 plant or plants held to be officinal by the London Col- 

 lege of Physicians ; the characters of a family neces- 

 sary to be known by the student are first given, then 

 the geographical relations of it, then its most generally 

 marked properties, medicinal or economical, and, finally, 

 the officinal plants yielded by it. 



EXOGEN^E OR DICOTYLEDONEJ3. 



Stem having a central cellular system or pith, the 

 woody matter existing in the form of compact zones 

 more or less concentric to the pith, the last-formed zone 

 being farthest from it. Leaves with a reticulated sys- 

 tem of venation and articulated with the stem. Floral 

 structures developed upon a quarternary or quinary 

 type. Embryo with two cotyledons and an exorrhizal 

 mode of germination. 



Though the above are the essential characters of the 

 plants collected under this grand division, we are not to 

 suppose that a case cannot exist in which one or other 

 of them may be found wanting, and yet the plant be 

 entitled to rank here just as well ; it is not so entitled 

 merely because it agrees in one or even two particulars 

 with the characters of the group, but because the gene- 

 ral combination of its characters is such, that on the 

 whole its affinity is distinctly traced, though it may 



