torical Society, whose scanty publications Thoreau sought and mastered, had existed for some ten years. Its botany and zoology were better known; but the terminology and classification of botany have so much changed in forty-four years that the scientific reader must look with charity on the lists of plants so industriously noted down by Thoreau. The text-books used by him were chiefly Asa Gray's Manual of the Botany of the Northern United States, and Alphonso Wood's Class-Book of Botany, illustrated by a Flora of the Northern, Middle and Western States. Both have been superseded by later works or newer editions; while for Minnesota alone the diligent researches of Professor Conway MacMillan and others have supplied a mass of details which make Thoreau's doubts and suggestions look at times almost puerile. But he was a naturalist who was also, like Linnæus, a poet, and even more profoundly poetic than the epoch-making Swede, whom he greatly admired, while viewing the mob of naturalists with humorous aversion. Their Latin and Greek terminology he styled "dead words with a tail,"
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