PRELIMINARY TREATISE. 
17 
it does or does not separate individuals which agree in 
another point of greater, or in more than one of equal, 
apparent importance. The individuality of kinds in the 
sexual creation rests on the possibility of their being propa- 
gated by union, and is limited by a secret impediment, pro- 
bably depending on the unsearchable adaptation of the 
minutest vessels through which that union is to be effected ; 
but the object of the limitation being to prevent the union of 
things dissimilar, there will be outward appearances to 
indicate the existing bar, and the skill of the botanist must 
be exerted to distinguish which are the features that are 
really symptomatic of the impediment, and which, from not 
being so, are unessential. Botany is therefore a science of 
conjecture in its fundamental office, the distinction of genera. 
We assume from observation and analogy, that certain points 
indicate an absolute diversity of kind; horticultural experi- 
ments bring the accuracy of those assumptions to the test, 
and either confirm or refute them, by proving the possibility 
of sexual intermixture to be, or not to be, limited in accord- 
ance with those points. The Almighty has allowed the 
several genera of vegetables to disport themselves in nume- 
rous forms of species and local or accidental varieties, which 
are more qr less capable of intermixture according to their 
constitute , and diversity, with various degrees of fecundity 
and sterility in the united produce. It seems to me utter 
waste of words to argue whether vegetables, if of one genus 
or identical kind, are species or varieties; if they are found 
different in a natural state and maintain their diversity when 
removed to different localities, they are usually termed 
species; if they return to the more general type when 
removed, or if the difference is trifling, they are properly 
termed local varieties, in contradistinction from cultivated 
and accidental variations. But this distinction is of very 
subordinate importance; it is a matter of convenience and 
opinion, and not of fact. The discrimination of genera, or 
identical kinds, by whatever term that identity shall be sig- 
nified, is the true basis of botanical labours. 
We are unable to ascertain when or how their subdi- 
vision took place into the numerous forms which now adorn 
the earth, and have been termed species and varieties. 
The various races of mankind were certainly distinguished 
at a very early period after the deluge, probably at the very 
time of the miraculous dispersion, and separation of tongues ; 
c 
