Thistles and Nettles 323 
In the hawthorne, the locust, and the wild orange- 
tree some of the lower branches develop into sharp 
spines which prick the noses of would-be assailants. 
In the bramble those hairs which clothe the stem 
of most plants have thickened into pointed prickles. 
In the holly the angles of the leaves have grown 
into needle-like points, which deter animals from 
browsing upon them, and it is noticeable that when 
the holly develops into a tree its foliage, carried 
up into comparative safety, becomes almost smooth. 
On the Irish gorse, a native of commons where 
cattle wander, and of mountain-slopes where half- 
starved sheep run wild, all the leaves are thorns. 
The green color of these thorns shows that they 
contain chlorophyll, and they fulfill the office of 
the foliage, which they have entirely supplanted. 
The whole gorse-bush, from its root to its crown 
of honey-sweet golden flowers, is one bristling de- 
fiance. 
The teasel (Fig. 91) is evolving its armor, which 
is already disconcerting to a browsing vegetarian, 
and which may become positively deterrent in times 
to come. Its leaves are supported by strong, mid- 
ribs, each of which bristles all down its length, with 
saw-teeth. The side-veins are studded with smaller 
teeth, and, while the lower sides of the leaves are 
