26 
all the plants which have been raised in the Arboretum during the last 
twenty-five years no individual which suggests hybrid origin has been 
noticed. Until the beginning of this century little attention had been 
paid to these plants by American botanists or gardeners. Some of the 
species were first named and described from plants cultivated in Europe, 
and one very distinct and interesting group of small shrubs, the Intri- 
catae, named for a plant growing in the Botanic Garden in Copen- 
hagen; of this group ninety species are now recognized and most of them 
will flower in the Arboretum during the next few days. The species 
of this group are most abundant in western Massachusetts and in New 
York, Pennsylvania and Michigan, that is in that part of the country 
which eighty or one hundred years ago was familiar to the most keen- 
eyed, industrious and systematic botanists and plant collectors which 
this country has produced. One hundred and fifty years ago or more, 
the so-called English Hawthorn, or May, was more often planted here 
than any of the native species, and it was with this plant that Wash- 
ington struggled to make a hedge at Mt. Vernon; an excellent gardener, 
he probably did not realize that the seeds of Crataegus do not germi- 
nate until they have been allowed to remain for two years in the 
ground, and as the seedlings did not appear when he expected them 
he dug up the seed-bed and planted something else. 
The two species of western Europe, Crataegus oxyacantha and C. 
inonogyna, and many of their varieties, are established in the Arbor- 
etum. These are the only foreign species which have ever been nat- 
uralized in North America where they are now abundant in some parts 
of Nova Scotia. Forms of this species with scarlet and pink flowers 
are conspicuous and are the only Hawthorns with colored flowers. The 
most beautiful, however, of all the foreign Thorns known in the Arbor- 
etum is C. pinnatifida from eastern Siberia and northern China. The 
large, deeply divided leaves make this one of the handsomest of the 
whole genus; the flowers are large and produced in profusion. A form 
of this species with larger leaves and much larger fruit (var. major) 
is cultivated in orchards as a fruit tree in the neighborhood of Peking. 
It flowers and produces its fruit here abundantly every year. 
One of the earliest, if not the earliest American species to flower, 
Crataegus arnoldiana, was discovered growing wild in the Arboretum 
on the wooded bank in the rear of the Bussey Institution. It grows 
also on the banks of the Mystic River in West Medford, Massachusetts, 
and near New London, Connecticut. This is one of the handsomest of 
the American Hawthorns and belongs to the Molles Group, which con- 
sists of trees distinguished by their large size, large early flowers 
which usually open with the unfolding of the leaves, and by the large, 
often edible, scarlet or rarely yellow fruits. That of C. arnoldiana 
ripens late in August or early in September and fruit can be found on 
other species of the group a little later in the year. There are several 
species of this tree growing from the valley of the St. Lawrence River 
in the Province of Quebec to Texas. They now are, however, more 
numerous in the region west of the Mississippi River and are almost 
entirely wanting in the southeastern states. In winter this tree is 
