for the advance of Botany. 121 
elaborating the minutest details in the history of every species it 
contains, he cannot fail of making some observations which may as- 
sist in approximating more closely to the discovery of the natural 
system. Independently of any formal attempt of this kind, every 
one who examines for himself is continually stumbling upon some- 
thing or other, which, if it were recorded, would assist in refining 
our systematic arrangements ; and such minor observations may al- 
ways find an appropriate place in the pages of a scientific magazine, 
when they might be considered too trifling for publication in the 
Transactions of any scientific society. 
The greatest desideratum in scientific botany next to obtaining a 
law for the determination of species, is' some criterion for establish- 
ing the relative values of those different groups into which species 
are collected, under the titles of Genera, Tribes, Orders, &c. 3 com- 
pared with some of the best defined and most extensive natural groups, 
such as the Composite, Leguminosse, Gramineae, &c. There are 
many others, considered as Natural Orders, which seem to possess 
very slight claims to be ranked with them as groups of equal value. 
The tendency at present appears to be more generally in favour of sub- 
dividing those which have been previously established, than of con- 
necting such as are most nearly allied. In the excellent publication 
of Nees ab Esenbeck, the " Genera Plantarum Florae German icas," 
this principle is carried to an extreme, and so far as it serves to point 
out the distinct groups, however numerous, into which species may 
be collected, nothing can be better. The next requisite is to know 
how to distribute these minor groups into larger ones, which the au- 
thor has also effected with great judgment. But still in the present 
state of the science, we have no certain knowledge whether the se- 
veral groups bearing the same name are truly of the same value. 
The difficulty which at present attends the construction of natural 
groups of similar value is forcibly exhibited by Mr Bentham in his 
excellent and elaborate monograph on the Order Labiatse. Under 
his genus Melissa, in which he includes Calamintha, Acinos, and 
Clinopodium of other authors, he observes,* " Whether the cha- 
racters be derived from the parts of fructification or from general 
habit, the circumscription of this and the nearly related genera of 
Hedeoma, Micromeria, Gardoquia, and Keithia, is attended with 
much difficulty ; and it might, perhaps, have been a clearer classi- 
fication, if the whole had been considered as forming one extensive 
genus, as in the case of Salvia, Hyptis, Teucrium, c. The relative 
proportion, direction, and size of the upper and lower teeth of the 
calyx, the hairs at the orifice, the proportion of the corolla to the ca- 
* P. 384. 
