a three-week excursion, showed his skill at locating and identifying rare species. In Baines's Flora of Yorkshire only four mosses were recorded from Teesdale. Spruce increased the record to 167 mosses and 41 hepaticae, of which six mosses and one liverwort were new to Britain.

In April, 1845, he published in the London Journal of Botany descriptions of 23 new British mosses, about half of which he had discovered himself. That year he also published his "List of the Musci and Hepaticae of Yorkshire"