18 
It cannot be said, however, that this investigation has been more than 
commenced and there are still great regions in the United States 
where Hawthorns are known to exist which have not yet been worked 
critically with reference to this genus. Some of the plants which these 
seeds sown at the Arboretum have produced have been arranged on the 
eastern slope of Peter’s Hill and others have been widely distributed 
in this country and Europe. There is a large collection also of Haw- 
thorns mainly obtained at the Arboretum in the parks of Rochester, 
New York, and there is one large Arboretum collection in England 
and another in France. In a few years, therefore, there will be a 
good opportunity for a comparative study of these plants from a botan- 
ical and horticultural standpoint, for last year some three hundred and 
fifty different species flowered on Peter’s Hill and probably this year 
a still larger number will produce flowers and fruits there. Of the 
species which have grown to a large size in the Arboretum and have 
proved themselves desirable garden plants may be mentioned Cratae- 
gus Arnoldiana, C. mollis, C. arkansana, and C. submollis. These 
belong to the Molles Group, in which the species are trees with wide 
heads, large early flowers and large, usually brilliant scarlet fruits. 
A large plant of C. coccinioides in the old Crataegus Collection, be- 
tween the Shrub Collection and the Parkway and near the Forest Hills 
entrance, has itself shown this year the decorative value of an American 
Hawthorn. It is a round-headed tree from the neighborhood of St. Louis 
with large flowers in very compact, nearly globose clusters and large 
round fruit ripening in the early autumn. In this old collection are 
other plants which are now large enough to show their value for the 
decoration of parks and gardens; from among them attention is called 
to C. Crus-galli, the Cockspur Thorn, which has perhaps been more 
generally cultivated than any other American species and is the type 
of one of the most distinct of the groups into which the genus is 
divided; C. nitida, a flat-topped tree with wide-spreading branches and 
narrow lustrous leaves. Although the flowers and fruits are compara- 
tively small, their abundance, the lustre of the leaves, and the habit 
of the tree make it one of the handsomest of the Thorns which can 
be successfully cultivated in this climate. C. pruinosa, C. aprica and 
C. succulenta are well represented here and are good examples of 
three large and distinct groups. C. pruinosa is a small tree with 
smooth bluish green leaves, large flowers made conspicuous by the 
large rose-colored anthers of the twenty stamens, and globose fruits, 
bright green and covered with a glaucous bloom when fully grown 
and turning scarlet late in the season. In all eastern North America 
there are few handsomer Thorns. C. aprica is interesting as one of 
the few hardy representatives of the Flavae Group which is entirely 
confined to the southeastern states with a few representatives ascend- 
ing into the valleys of the southern Appalachian Mountains. It is not 
one of the handsomest species of the group for the flowers are not so 
large as those of many others, and the anthers of the ten stamens are 
yellow. C. succulenta is a showy representative of the Tomentosae 
Group which is one of the largest of the northern groups and is spec- 
ally beautiful in autumn when the branches are covered with large 
clusters of drooping scarlet translucent fruits. Two black-fruited 
