31 
Arnold Arboretum Hybrids. Except with Roses, no attempt has 
been made at the Arboretum to produce hybrid trees or shrubs. Sev- 
eral hybrids, however, have appeared here from time to time, and the 
following, of which descriptions have been published, or will be pub- 
lished, are now well established here. Such hybrids are always inter- 
esting, and among those which have appeared in the Arboretum are a 
few which are more valuable than their parents, and in two instances 
at least the handsomest garden plants in the genera to which their par- 
ents belong. The Arboretum hybrids are Pterocarya Rehderiana, Sor- 
hus arnoldiana, Forsythia intermedia primulina, Malus arnoldiana, 
Malus ruhrijiora, Malus Dawsoniana, Prunus arnoldiana, Pyrus con- 
gesta, Cornus arnoldiana, Betula Jackii, Viburnum Jackii, Berberis 
notabilis, Lonicera amoena arnoldiana, and Aesculus Harbisonii. An- 
other Barberry, Berberis ottawensis, believed to be a hybrid of Ber- 
beris Thunbergii and B. vulgaris, which was first described from a 
plant in the Arboretum connected with the Dominion Experimental 
Farm at Ottawa, has appeared several times among seedlings in this 
Arboretum where it has proved to be a handsome and distinct plant. 
There is a large specimen of this hybrid on the right-hand side of the 
entrance to Azalea Path from the Bussey Hill Road. The most valu- 
able of the Arboretum hybrids for general cultivation in this part of 
the world are Pterocarya Rehderiana, Malus arnoldiana and Sorbus 
arnoldiana. The Pterocarya, which is evidently a hybrid of the Cauca- 
sian P. fraxinifolia and the Chinese P. stenoptera, is much hardier 
than its parents and has grown more rapidly in the Arboretum than 
any of the species of this interesting genus of the Walnut Family. 
Several of these hybrid plants appeared here in 1879 from seeds sent 
from the Arboretum Segrezianum in France as seeds of P. stenoptera, 
so that although the plants were raised here the crossing of the two 
species occurred in France. The grove of these trees which shades a 
stretch of Hickory Path near Centre Street is one of the most inter- 
esting and attractive groups in the Arboretum. The trees send up many 
suckers from the roots and for several years have flowered freely and 
produced fruit. This hybrid is an important addition to the number of 
interesting and handsome trees which can be successfully grown in this 
climate. Sorbus arnoldiana, which appeared here in 1907 among seed- 
lings of Chinese Sorbus discolor, is a fast-growing, vigorous tree already 
nearly twenty feet tall, with smooth, lustrous, yellow-gray bark, erect 
branches forming a broad compact symmetrical head, leaves with the 
narrow leaflets of Sorbus discolor, and the compact, slightly convex 
flower-clusters of Sorbus Aucuparia, as broad as those of S. discolor. 
The fruit is pink and in color unlike that of any of the species of Sor- 
bus. This hybrid is the handsomest Mountain Ash in the collection 
where it has grown more rapidly than most of the species of the genus; 
and there now seems to be every reason to hope that it has enabled 
the Arboretum to add to the list of ornamental plants hardy in New 
England another tree as valuable as Malus arnoldiana. This tree, 
which appeared in the Arboretum many years ago, has been so often 
noticed in these Bulletins that it is not necessary now to do more than 
to repeat the fact that it is probably a hybrid of Malus Jloribunda and 
some other Asiatic Crabapple, probably one of the hybrids of Malus 
baccata; and that, in the judgment of many persons, it is the hand- 
