AMERICAN 
MEDICAL BOTANY. 
| 
GILLENIA TRIFOLIATA. 
Common Gillenia. 
PLATE XLI. 
Nowrwrrnsraxpine the principle avowed by 
Linneeus, that genera are formed by nature ; the 
determination of generic consanguinity in species 
occasions in many instances one of the greatest 
perplexities of the botanist. What difference in 
structure and external form either of flower or 
fruit, is sufficient to separate families of plants 
from each other ; is a point often difficult to decide ; 
and is perhaps as frequently set at rest by conve- 
nience and by arbitrary decision, as it is by any 
unexceptionable boundaries designated in nature. 
When the species of a vegetable order are exceed- 
ingly numerous, and a close similarity pervades 
the whole; genera are multiplied by botanists, 
that the discrimination of species may be facilitat- 
