162: PRINCIPLES OF BOTANY, ETc. 
§ 146, 
The flower and fruit are the most constant parts 
of plants, and therefore on them should a System be 
built, and from them should the characters be se- 
lected. Some botanists have employed the leaves 
for this purpose; but experience shews how falla- 
cious such a system proves. As the flower is the 
chief foundation of System, it affords likewise cha- 
racters for establishing the Genera. ‘The Species, 
however, must be distinguished by other chaFaciers. 
than those taken from the flower. 
§ 147. 
The first rule, which naturally arises from the 
foregoing observations, is this, that the characters 
of the class must never be the same with those of 
the orders, nor the characters of the orders the 
same with those of the genera; but that the genera, 
which stand under one order and class, must pos- 
sess the characters of these without exception; as 
for instance the potatoe, Solanum tuberosum. ‘This 
plant stands in the fifth class of the System of Lin- 
necus and first order: the characters of the fifth 
class are five stamina, and of the first order one 
style: the genus Solanum has the following charac- 
ters: a quinquefid calyx, a ed corolla, 
and a bilocular berry with many seeds. Thus if we 
place the discriminating character of the genus in its 
having five stamina and one style we would trans- 
eress the rule, for these chavaciars are common not 
only 
