The Tacamahac or Balsam Poplar (_Populus balsamifera_) is another importation from North America, introduced in 1692. In its native country it grows to a height of eighty feet, but here forty or fifty feet is more usual. Its leaves are of more slender form than those of the other Poplars, egg-shaped, with a near approach to being lance-shaped. Their edges are toothed, their upper surface dark green and smooth, the underside whitish with cotton. The distinctive character of the tree is the fragrance of its foliage, which scents the air on moist evenings, and makes the Tacamahac a desirable tree to plant near the water, where alone it attains any moderate size. The Willows (_Salix_). There is not in the whole of the British flora another genus of plants that presents such difficulties of identification as the genus _Salix_. Even so hardened a botanist as Sir J. D. Hooker, in reviewing the tangle of species, varieties (natural and cultivated), and hybrids, is so far stirred from his ordinary composure that he stigmatizes it as a "troublesome genus." When Sir Joseph chose that mild adjective he was at Kew surrounded by the national herbaria and with nicely labelled living plants at hand for comparison. What, then, can the rambling nature-lover hope to do with the Willows he comes across one at a time, without much chance of comparing? He must be content to follow the "lumpers," who group a number of these uncertain forms under the name of a species to which they have evident relationship. When he has mastered the distinctions between these aggregate species, it will be early enough to attempt the segregation of the forms and varieties under each.