67 
place in the garden. K, polifolia^ or glauca^ is hardy, but not easy to 
establish in gardens. The Kalmias, like the Rhododendrons and all 
plants of the Heath Family, cannot grow where there is lime in the soil. 
Rhododendrons. A large number of the species and hybrids of Rho- 
dodendrons are now cultivated in California and in some parts of 
Europe, but only a few of them can be grown in the open ground in 
the eastern United States, and the region here where any of these 
plants thrive is not large, for it is too cold for Rhododendrons north 
of Massachusetts and too hot for them south of Pennsylvania except 
on the slopes of the Appalachian Mountains, Only the species of east- 
ern North America, R. maximum, R. catawbiense, carolinianum 
and R. minus, and R. Smirnowii of the Caucasus, R, hrachycarpum 
of the high mountains of Japan, and R. micranthum from western and 
north central China are perfectly hardy here. This last is a small 
plant with small leaves and small compact clusters of white flowers 
and looks more like a Ledum than a Rhododendron. Of the sixty 
odd species of Chinese Rhododendrons raised at the Arboretum from 
seed collected by Wilson this is the only one that is perfectly hardy 
here, although R. discolor can be kept alive in sheltered positions at 
least for a few years. Two little European Rhododendrons, R. fer- 
rugineum and R. hirsutum live here but the plants are generally 
short-lived and not really satisfactory. Most of the Rhododendrons 
cultivated in this part of the country are hybrids of R. catawbiense, 
but only a very few of the great number of these hybrids which have 
been raised in Europe are really hardy here. There are hybrids, too, 
growing in the Arboretum of R. Metternichii, of R. Smirnowii, of R. 
maximum, of R. minus and of the European species which are hardy. 
There is still much to be accomplished in the gardens of eastern America 
by the breeders of hardy Rhododendrons. 
Hollies. Eex opaca, the widely distributed, red-fruited species of 
eastern North America is the only broad-leaved evergreen which is 
a tree in this climate. Ilex opaca seems able to flourish under the con- 
ditions of city life and to be little injured by the smoke from bitu- 
minous coal fires which are so injurious to most evergreen plants. That 
it is a long-lived tree is shown by the specimens planted by Washington 
about 1785 at Mt. Vernon which are still in perfect health and among 
the most interesting of the trees planted by him, Eex glabra is another 
excellent broad-leaved evergreen for the decoration of New England 
gardens. It is a broad round-topped shrub with small lustrous leaves 
and small black fruit a good deal hidden by the foliage, and is a native 
of the coast region from New Hampshire to Texas. A good mass of 
these shrubs can be seen on the right hand side of the Hemlock Hill 
Drive opposite the Laurel plantation. Two Japanese evergreen Hollies 
can be grown here. Ilex crenata and I. pedunculosa. The former is a 
small bushy tree or small shrub with small finely toothed leaves and 
small black fruit borne on such small stems that it is hidden by the 
leaves. There are forms of this plant with larger and with smaller 
leaves, and the small-leaved form (var. microphylla), on which the 
leaves are not more than half an inch long, is the hardier. Several 
