LAEGE GENEKA AND VAEIABLE SPECIES 455 
or a few well marked unvarying species, especially if its 
generic name is a very familiar one, hence Amygdalus, 
Prunus, Cerasus, are kept up, though certainly not good 
genera in a scientific view of Eosaceae. Few plants are more 
variable than Hawthorn — it is a small genus dismembered 
from Pyrus, but no British author makes varieties of it. 
Genera in short are almost purely artificial as established 
in Botany : some are objective like Salix and Bosa, i.e. every 
ignoramus recognises them and they are called natural 
genera, good genera, &c., &c. Others are suhjective, they 
require a special knowledge of the Order to which they 
belong to know them — ignorami do not recognise them : 
such are genera of Grasses, Cruciferae, Umbelhferae, &c. 
But between what the ignoramus does recognise and does 
not there is no limit ; and the first rate Botanist, working 
upon a partial knowledge of a group, is only in the position 
of an ignoramus after all. His two very distinct groups of 
an Order are to him two genera ; had he the whole species 
of the Order he would never have recognised the groups at 
all, as groups. This is a terrific screed. 
[Darwin replied on February 28 (M.L. i. 105) and March 11 
(CD. ii. 102), and Hooker responded] : 
March 14, 1858. 
I quite see in what respects local Floras are much the 
best suited to your purpose ; or rather, how they would he so, 
if they were worked out upon the same principle as the general 
Floras, but the fact that they are not so, and that they are 
hotbeds of bad big genera, is a very serious objection to the 
use of them. 
I shall be however most curious to see the results of 
Bentham's British Flora. He reduces the Eubi to 6 species, 
I think (and about 11 varieties, I suppose), which gives 
you a small very variable genus, whilst Babington has 
28 species or so, besides varieties — so Callitriche, of which 
Babington has several species but which Bentham reduces 
to 1 with 2 ? varieties. You must however take care not 
to get entete with your results. I shall certainly go over 
the Tasmanian Flora for your sake, and see whether or no I 
should not have noticed varieties to many small genera, to 
make their species consistently worked with the big. I am 
