REVIEW AND CONCLUSION 



SYSTEMATIC 



When discussing the nomenclature of plants in 

 chapter xii, we saw that species could be grouped 

 into genera by characters which are less likely to 

 have been modified in the course of ages to suit 

 the special conditions of the plant's life, than are 

 the leaves and general habit. We have now learnt 

 that genera may also be grouped into families, or 

 NATURAL ORDERS as they are also called, the mem- 

 bers of a family being alike not only in the general 

 arrangement of the leaves (opposite or alternate, 

 decussate, bifarious, etc.), and in the number and 

 arrangement of the parts of the flower, which are 

 the more definite characteristics, but also in such 

 peculiarities as interpetiolar stipules (RUBIACE^E), 

 translucent oil-glands in the leaves (RUTACE^E, HY- 

 PERICINE^E and MYRTACE^E), a very resinous juice 

 (ANACARDIACE^), sticky latex (APOCYNACE^E and AS- 

 CLEPiADACE^e), a tomentum of brown hairs on the 

 young parts (RHAMNE.E and STERCULIACE^E), hood- 

 like stipules which completely cover the bud and leave 

 a scar extending right round the axis (MAGNOLIACE.E), 

 and peculiar venation (MELASTOMAC^E). 



There are other characters which though not com- 

 mon to all the members of a family, or confined 

 to it alone, are yet very distinctive. Practically 

 speaking all trees with bi-pinnate leaves and small 



