THE WILl.OV/S. 
6i 
The Black Italian Poplar {Popuhis monilifera) is another mis- 
named tree, for it is a native of North America, though introduced 
to England from the Continent in 1772 by Dr. John Hope. It 
has the distinction of being considered the most rapid-growing 
even of the Poplars. Loudon gives its rate of growth in the 
neighbourhood of London as between thirty and forty feet in seven 
years ! Even in Scotland (where it has been largely planted as 
a substitute for Larch, since the partial failure of that tree) it 
attains a height of 120 feet in sixty years, when planted along 
the river banks. It is probably only a variety of P. 7 iigra, 
which it resembles in most points, but is larger, and of very 
erect growth. 
The Tacamahac or Balsam Poplar {Populus balsainiferd) 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 (Sa/ix). 
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 
tiational herbaria and with nicely labelled living plants at hand 
