BOTANICAL SOCIETY OF LONDON. 
9 
plants may be known from the knowledge of the London 
genera. Also that six thousand plants of the whole number 
on the earth, may be safely ascribed to their proper 
genera, supposing the whole number of vascular species to 
be sixty thousand ; and this can be done by any Botanist 
who is well acquainted with the genera that grow within a 
moderate walk of his own residence. Even the Flora of a 
moderately extensive parish will generally embrace one-half 
of the species and two-third of the genera to be found in the 
kingdom. 
As genera have been shown to occupy a much larger extent 
than species, or are more extensively dispersed over the 
earth, in like manner orders are more widely diffused than 
genera. 
For example, all the orders of British plants are found in 
the vicinity of London, limited as before, except twelve ; and 
these twelve orders barely comprehend eighteen British spe- 
cies. Consequently the ordinal characters of all British vas- 
cular plants may be learned from such as are found within a 
moderate walk of this city. Also the ordinal characters of 
all the Northern European species, and most of the Austrian 
and French may be acquired from the British orders. Four 
thousand of the Equinoctial plants of America may be re- 
ferred to their families, in the same manner, and above 
thirty thousand species of known and described individuals. 
These facts prove that the study of a district Flora is of no 
mean importance, when we consider that by its aid we are 
enabled to decide on the genera of six times the number of 
species the said district supplies ; and on the orders of 
thirty times the amount of its productions. And while the 
student is learning the characters and uses of the plants, in 
his own neighbourhood, he is acquiring the same knowledge 
of all such as agree in genera and ordinal characters, amount- 
ing to many thousands. 
The utility of Local Botanical investigation may also be 
estimated by its relation to national and general Floras, 
which could scarcely be produced without the assistance of 
resident Botanists or district Floras. 
If we take a retrospective view of the progress of this 
science since its revival or rather its commencement among 
us, in the times of Queen Elizabeth, we shall perceive that 
the. value of Botanical localities was known at that early 
period. 
Gerarde, the author of the English Herbal, usually re- 
