AGEEEMENT AS TO LARGE GENERA 459 
* think the influence of associations of this and other^sorts on 
descriptive systematists. 
On re-reading your MS., I find the same objections as 
before, viz., that you overrate the extent of my opposition to 
your method. My great desire was to put every possible 
objection as strongly as I could. I did not feel myself a 
dissenter or opponent to your views, so much as a non-con- 
senter to them in the present state of my knowledge, nor till 
you had weighed my objections which I thought of greater 
weight than I do now. 
July 15 [1858]. 
The E.I.C. Examinations are cutting my time to shreds 
which must account for some of the incoherence of the fore- 
going. I have had more time for thinking over the subject 
at odd half hours and have endeavoured to grapple with the 
whole question. That point of the hypothetical behaviour 
of large genera when on the decrease puzzles me. 
As a corollary to your law, large Natural Orders should 
have fewer genera in proportion to species than small ; i.e. 
fewer definable groups. Cruciferae, Compositae, Umbelli- 
ferae and Grasses bear you out in this— true no end of genera 
are made in them, but they are bad— other Natural Orders 
are opposed. 
I thmk I have thought of a better reason than you give 
for whole Nat. Ords. being worse for your purpose than local 
Floras— viz., 1. That conditions do not go on varying with the 
area beyond a certain point ; there are limits to the combina- 
tions of climate and soil. A genus inhabiting 1000 square, 
miles will survive such and such conditions and under their 
influence form x species ;— all these conditions may occur in 
100 miles of the said area, and adding the other 900 miles adds 
no more conditions. 2. Many large genera are absolutely 
confined to the tropics or to temperate regions or to dis- 
tricts and do not stand in the same relation to one another as 
the mundane genera do. This I think you have expressed, 
but not more clearly than I have. This would lead me to 
suggest the propriety of working one or two of your Floras by 
purging them of stragglers and such plants generally as are 
typical of other climates and exceptional in this— of stragglers 
in short— e.g. Panicum. I think this process would intensify 
your results. 
