BOTANICAL APHORISMS,. 173 
§ 159. 
Number alone can never constitute genera, and must 
never be considered as of any importance. 
Nothing is more subject to variation than the 
number of the stamina. Whey are often very va- 
tious in the same genus. Some plants, when they 
grow in arich soil, acquire one or two additional 
stamina and even additional petals. Often they are 
found with double the number of stamina they 
ought to have; for instance, a plant has ten sta- 
mina that should only have five; or contrariwise, 
it has only five stamina when it should have ten. 
Two often vary into four, three into six, four imto 
eight, five into ten, six info twelve; in this way the 
number is either increased’ or diminished. When 
the structure. of the other parts perfectly corres- 
ponds. with another genus, and differs only in the 
number of a part of the flower, whether it be calyx, 
corolla, stamina or style, it would be improper on 
that account to make it a new genus. 
§. 160. 
When the number in all the parts of a flower is 
constant, it may be used as a subordinate generic cha- 
racter, but with great caution. 
This rule must be used’ with great prudence. if 
it can be avoided, number must not’ be resorted to. 
Liinné has given: one example’ of this rule in the 
genera of Potentilla and Tormentillas Number dis- 
tinguishes these two artificial genera: the first: has.a 
double pentaphyllous calyx and a‘ pentapetalous co- 
| rolla. 
