BUDDING, GRAFTING, LAYERING.—SPINES OR THORNS. 107 
of being separated from their parents and attached to other in- 
dividuals of the same, or even of nearly allied species ; or a 
branch with one or more buds upon it may be bent down into 
the earth (fig. 230). The operations of Budding, Grafting, and 
Layering depend for their success upon this circumstance ; and 
in some plants buds naturally separate from their parents, and 
produce new individuals. These operations are of great import- 
ance in horticulture, because all plants raised by such means 
propagate the individual peculiarities of their parents, which is 
not the case with those raised from seed, which have merely a 
specific identity. 
1t sometimes happens that a leaf-bud, instead of developing 
as usual, so as to form a symmetrical leaf-bearing branch, be- 
Fic. 210. Ley PAE Pres22. 
Fig. 210. Branching spine of the Honey Locust (Gleditschia). Fig. 211. 
Spine of a species of Thorn.— ig. 212. Leafy spines of the common Sloe. 
comes arrested in its growth, and forms a hardened simple or 
branched projection terminating in a more or less acute point, 
and usually without leaves, as in Thorns (fig. 211), Gle- 
ditschia (fig. 210), and many other plants. Such an irregularly- 
developed branch is cailed a spine or thorn. That the spines 
are really modified branches is proved not only by their struc- 
ture, which is exactly the same as the stem or branch upon 
which they are placed, but also by their position in the axil of 
leaves ; by their sometimes bearing leaves, as in the Sloe (fig. 
212) and Spiny Rest-harrow ; and by their being frequently 
changed into ordinary leaf-bearing branches by cultivation, as 
in the Apple and Pear. Spines are sometimes confounded 
with prickles, already described (page 66), but they are readily 
distinguished from these by their structure and connexion 
with the internal parts of the stem ; the prickles being merely 
