BOTANICAL APHORISMS. 189 
When two plants differ from one another only in 
the colour of the flower, in having a different smell 
or taste, in one being a foot, and the other a cubit 
high ; or in the one having a smooth and the other 
a hairy leaf or stem; such plants can be considered 
merely as varieties. If one plant differs from ano- 
ther in all these qualities together, it may pass for a 
different species. | 
White or black spots on the leaves of the plant 
cannot discriminate species, and should only be taken 
into account when plants really different cannot be 
distinguished otherwise. But if a species can be 
ascertained without having recourse to colour, it is 
always better. 
Smell and taste, as they are only comparative qua- 
lities, cannot be received as specific characters. 
The size depends so much on the quality of the 
soil that no regard can Le had toit. The pubes- 
cence is exactly in the same circumstances; for a 
hairy leaf will become smooth in a different soil. 
Plants with tomentose, spiny or woolly leaves or 
stalks, are not so easily considered as Varieties, and 
these qualities afford the best distinctions. 
§ 184. 
The root gives a beautiful and infallible mark for 
distinguishing species. 
When the root in two similar plants is different, 
they may be considered as different species. Culti- 
vated plants are indeed an exception. Culture for 
a length of time, or the skill of a gardener, often 
. give 
