70 
SILVA OF NORTH AMERICA. 
ROSACEA. 
Many insects’ feed upon the different species of Pyrus, which are also subject to serious fungal 
diseases.” 
Pirus, the classical name of the Pear-tree, was changed to Pyrus by Tournefort,’ and then adopted 
by Linnzus, who, in establishing his genus, united with Pyrus the Cydonia‘ and Malus® of Tournefort. 
forests of northern Europe and Asia, in the mountainous regions of 
central and southern Europe, and of central, southern, and western 
Asia. It is valued by planters for the beauty of its entire or vari- 
ously divided ample leaves, which are pale or sometimes nearly 
white on the lower surface, and for its subacid and astringent fruit, 
which is a favorite food of birds, and is sometimes made into flour 
and often fermented into a kind of beer or distilled into a powerful 
spirit. 
The wood of the White Beam-tree is hard, strong, and durable, 
and is largely employed for the handles of tools and the bearings 
of machinery, and by wheelwrights and turners (Loudon, Arb. Brit. 
ii, 910. — Mathieu, Flore Foresti¢re, ed. 2, 123). 
1 Many of the insects which injure the different species of Pru- 
nus in America also attack the native Apples, and Mountain Ashes 
are sometimes seriously injured by them. ‘Tent-caterpillars and 
the larve of Tussock-moths are often abundant on the Apple, and 
the Mountain Ash suffers from attacks of the Fall Web-worm 
(Hyphantria cunea, Drury). Datana ministra, Drury, often com- 
pletely defoliates the branches of small trees, and Gidemasia con- 
cinna, Smith & Abbot, commits similar depredations. Great destruc- 
tion among the trees of this genus, and often their death, is caused 
by borers. The Apple-tree Borer (Saperda bivittata, Say) and the 
Flat-headed Borer (Chrysobothris femorata, Fabricius) are the most 
destructive to the Apple and the Mountain Ash. Several Scale-in- 
sects affect the bark and branches, the most harmful being the 
Scurfy Bark-louse (Chionaspis furfurus, Fitch) and Mytilaspis pomi- 
corticis, Riley. The foliage is also injured by Aphids, and the fruit 
of the Wild Apple by the ravages of the Codlin-moth and a Cur- 
culio (Anthonomus quadrigibbus, Say). No less than eighty-one 
species of insects which attack the cultivated Apple in America are 
enumerated by Saunders (Insects injurious to Fruits, 18), and most 
of them may be discovered on. the wild species also. 
? Of the Fungi which attack the North American species of 
Pyrus, the most interesting are the different Restelie, found on the 
leaves and less frequently on the fruit and young stems of most of 
the species. The Restelice, commonly called Cluster-cups, belong 
to the order Uredinee or Rusts, a group of plants which pass through 
several different stages in their development, in some of the stages 
appearing as parasites on certain genera of flowering plants, while 
in others they may be parasitic on entirely different genera. In the 
most highly differentiated Rusts there may be as many as four dif- 
ferent stages during their development. The most destructive of 
these plants to our Wild Apples is Restelia pyrata, Thaxter, a Clus- 
ter-cup which usually grows in dense rings on the under side of the 
leaves of Pyrus coronaria, and sometimes on those of Pyrus angus- 
tifolia and several of the native species of Crategus, and in a less 
striking form on the leaves of the cultivated Apple-tree. This 
species is peculiar to North America, and its teleutosporic stage is 
reached in the large yellow gelatinous masses common on the young 
branches of the Red Cedar in May. In the northern part of the 
country the leaves of the Mountain Ash, Pyrus Americana, exhibit 
large yellow spots, and on their under surface bear groups of long 
narrow Cluster-cups which appear identical with those of the Euro- 
pean Restelia cornuta, Fries, although as yet the teleutosporic stage 
of this plant has not been detected in North America. Other fungi 
which attack the American species of Pyrus are Entomosporium 
maculatum, Levéillé, with curious ciliated spores, found commonly 
on the leaves of Quinces, Pears, and Apple-trees, as well as on Ame- 
lanchier and several species of Crategus ; and Nummularia discreta, 
Tulasne, most common on the branches of the Apple-tree, but 
sometimes seen on those of Pyrus Americana. 
8 Inst. 628, t. 404. 
4 Inst. 632, t. 405. 
5 Inst. 634, t. 406. 
CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT SPECIES. 
Matvs. 
3 to 5, more or less united below. 
leaves, involute in vernation. 
Calyx-lobes persistent ; fruit depressed at the base. 
Flowers in simple umbellate or racemose cymes on spur-like lateral branches; styles 
Trees with small winter-buds, scaly bark, and simple 
Leaves ovate, truncate or subcordate at the base, incisely serrate, often lobed, membra- 
naceous soe . 
Leaves lanceolate-oblong, acute at the base, crenulate-serrate, or nearly entire, sub- 
CORIACOOUSI ass te hey Tone esi htc ae 
Calyx-lobes deciduous; fruit not depressed at the base. 
Leaves ovate-lanceolate, serrulate, often 3-lobed 
Sorpus. 
Flowers in compound leafy cymes; styles usually 3, free. 
- id. P. coronaria. 
- . . . 2 P, ANGUSTIFOLIA. 
a4 eee aaa 3. P. RIVULARIS. 
Trees with large winter- 
buds, smooth aromatic bark, and odd-pinnate leaves, the leaflets conduplicate in vernation. 
Leaflets lanceolate, acuminate. . .. .. . 
Leaflets oblong-oval to lance-ovate, mostly obtuse . 
4, P. AMERICANA. 
5. P. SAMBUCIFOLIA. 
