BOTANICAL APHORISMS. 193 
be two, three or more, isan uncertain character. In 
general it may be observed, that nothing is so in- 
constant, as number, and-that it ought never to be 
founded, on. 
§, 191. 
A species is never to be made a variety, nor ava- 
riety @ species, on account of any small di ifference. 
We shall see by the history of our, science, that. 
in the 17th and in the beginning of the 18th cen- 
tury, every inconsiderable variety of a plant was 
made a species, which led to great error. It is a 
rule, rather to take. a plant for a variety, than to 
make it too easily a species. 
Sp192: | 
The selected characters of a. species must be con- 
spicuous, in the varieties. 
If a plant is subject to great hem the cha- 
racters must be so, chosen that they may be seen 
in all its varieties. It would, therefore, be faulty 
to separate a plant that commonly has a five-lobed 
leaf, and. varies with an intire leaf, from. another 
plant, merely on account of its five-lobed leaf. In 
this case we must seek for other characters, otherwise 
the beginner, who has seen nothing but the variety, 
will never come to the knowledge of the species. 
§ 193. 
The characters, by which all the. species of a genus 
are distinguished, must be taken from one or a few parts. 
. : In 
