From H. C. Watson   23 February [1858]¹

My dear Sir

I do not express an opinion by any means positively;—but my impression is that botanists are more apt to letter & name varieties in large genera than in small ones.

Whether they have done so is a matter of fact, which could be ascertained by patience & time. But this would not show whether they followed external nature, or acted on an internal bias, in the course found to have been adopted, whichever it turned out to be.

Make the distinction between the “lumpers” & “splitters” of species. The former reduce species into var^s. & very likely do this more in large than in small genera; the large genera affording more debateable “forms”. The splitters raise varieties into species; thus leaving minor varieties only, to be lettered & named as varieties. I incline to the idea that the same taste or tendency which makes the splitters look out for many species in large genera, also makes them look out for varieties there.

One tendency in botanists seems pretty certain, & may vitiate conclusions deduced from numbers in reference to varieties. Say, that a species has one or two varieties, not up to the mark of sub-species, but still easily described: they are pretty sure to be named & lettered, one or both. Say, that another species has many varieties of like grade or character: they are passed by as too numerous for record.

Take three or four examples from last edit. of Bab. Man.²

Plantago lanceolata— “A very variable plant”— No var^s. named, lettered, or desc^d.

Polygonum aviculare— “Extremely variable”. No var^s. specified, except one because given as a species by Cont^l. bot^s.

Euphrasia officinalis— “A peculiarly variable plant, perhaps including 2 species”— Only the 2 mentioned by name, &c.

Saxifraga hypnoides— “These var^s. are scarcely worth notice.”— They are species in Smith,³ but lumped by Bab.

There is considerable caprice among technical botanists. Under one species or genus they will describe varieties;—while under another, they pass unnoticed equivalent or corresponding varieties. For instance, they will make a variety b glabra or b hirsuta under one species,—while under another equally & similarly varying, the smooth & hairy varieties are mentioned without greek letters or latin names, or not even mentioned at all.—

Very truly | Hewett C. Watson C. Darwin | Esq