ROB 
ROS 
close, and if the outside can be filled with 
a double row of some other fast-growing 
trees, at least on the windward side, it 
will be of assistance to the acacias in 
preserving them from damage at a future 
stage. There are several varieties, dis¬ 
tinguished either by their habit or the 
colour of their flowers: among the most 
beautiful— luteo, yellow; macrophylla, 
white; monstrosa, white and red; pendula, 
pink; and spectabilis, white. Robinia 
hispula, the Rose-acacia is an admired 
ornament of the shrubbery, it is a low- 
growing tree with spreading branches, 
which are clothed with dark red hairs 
while young, handsome pinnate leaves, 
and copious racemes of large deep rose- 
coloured flowers. It requires a sheltered 
position, or the branches are very liable 
to injury from heavy winds; on this ac¬ 
count it is generally kept comparatively 
dwarf by pruning. A very suitable posi¬ 
tion, in which the flowers are finely de¬ 
veloped, and the tree seen to advantage, 
is when trained against a wall or espalier 
frame; its otherwise straggling habit is 
not then perceivable, and every branch 
can be preserved. This species seldom 
produces seed, and the usual mode of 
propagation is by grafting upon stocks of 
the common acacia. The union is made 
in the ordinary manner of whip-grafting, 
but it must be done very low, in fact, a 
few inches below the surface of the soil 
is better than above it, the object being 
to keep the tree as dwarf as possible, 
and to prevent a severance of the graft 
from the stock; for when the plant is 
grown up, it is extremely probable, if 
worked upon a taller stem, that the en¬ 
tire head may be blown off. The rose- 
acacia succeeds best in a rather poor, 
light soil, and if the points of the shoots 
are taken off annually, it will put forth 
numerous spurs on the lower parts of 
the branches, which produce flowers, and 
render the tree compact in form. Three 
varieties are cultivated, the finest of 
which is macrophylla , with deep red 
flowers; the others are nana , aneat-grow- 
ing plant, with pink flowers, and rosea, 
which has its blossoms a shade or two 
darker than those of the species. The 
other hardy Robinias are davurica, with 
white and red flowers; dubia, which re¬ 
sembles it; and viscosa, approaching 
more nearly to A. pseudacacia, having pale 
purple flowers, but has a neuter habit 
of growth, on account of its smaller 
branches, which are clothed with hairs, 
in the manner of hispida, but shorter, 
and clammy with a viscid juice while 
young. All the Robinias are deciduous, 
losing their leaves among the first in 
autumn, and reproducing them late in 
spring. 
ROSA, Rose (Linn.) Nat. Order, 
Rosacea. This flower, by its beauty and 
fragrance, has engaged attention from 
the earliest periods of civilization, and 
though cultivated almost unremittingly 
throughout, is even yet capable of afford¬ 
ing novel varieties. The name of the 
family is derived from the Armorican 
rhos, or Celtic rhod, both signifying red, 
the prevailing colour of the original 
species. Botanists of the present day 
enumerate about one hundred and forty 
species and subspecies, whose geogra¬ 
phical distribution extends over a great 
portion of the earth’s surface; they are 
found in nearly all the cooler regions of 
Africa, Asia, North America, and are 
common throughout Europe. In the 
RosarumMonograpliia of Bindley, they are 
divided into ten sections, distinguished 
by some permanent characteristic—as in 
§ 1, Feroces, the branches are clothed 
with a tomentum, have numerous thorns 
and bristles, and smooth, naked fruit. 
§ 2, Bradeala, is distinguished from the 
above by its woolly fruit, shining leaves, 
and having a pair of small thorns beneath 
the stipules; the Macartney rose is an 
example. § 3, Cinnamomea, is known by 
the erect habit of the plants, their long 
lanceolate leaflets without glands, and 
their small, round, red fruit; the common 
cinnamon rose will be recognised in this. 
§ 4, Pimpinettifolia, the absence of 
bracteas to the flowers, and of stipular 
prickles, together with a greater number 
ol leaflets, and difference in habit, dis¬ 
tinguish this group, the type of which 
is the Scotch rose. § 5, Centifoliae, con¬ 
tains the most ornamental of our garden 
roses ; the group is known from the pre¬ 
ceding divisions by the thickened disc, 
6 
