In the matter of hardiness the American R. cataw-
biense has been the greatest of all gifts in the realm
of Rhododendron, and the hardiness of our present-
day race depends almost solely upon the dominant
influence of the blood of this species.
Rhododendron caucasicum is native of the higher
Caucasus peaks and should be of much value to us
since it is quite hardy in New England. Unfortu-



266 ARISTOCRATS OF THE GARDEN

natdy it has been very little used by hybridists but
such offspring as Boule de Ni^» Coriaceum, Jack-
sonii, and Mont Blanc are very satisfactory plants in
the Arnold Arboretum.
Our native R. maximwru though the first species
introduced into cultivation, has played a very unim-
portant part in the evolution of present-day Rhodo-
dendrons. In a manner it has been disappointing,
yet it is questionable whether it has had a fair chance.
To us its hardiness and late flowering are qualities
of vast import.
The first authentic hybrid is considered to have
arisen accidentally about 1820, between R. ponticum
and R. nudiflorum (an American species of the Azalea
section), and is still in cultivation under the names of
R. odoratum and i?. azaleoides. About the same time^
/?. catawbiense was crossed with R. ponticum but the
results were unimportant. Other early hybrids were
Hybrid Maximum (i?. ponticum x R. maximum) and
Caucasicum album (i?. ponticum album x R. cau-
casicum).
The earliest-introduced species were lacking in
color and their hybrid offspring had the same defect.
