124 ELEMENTS OF BOTANY 
attacks of grazing or browsing animals, have acquired what 
have with reason been called weapons. Among the most 
conspicuous of these are thorns, which are often modified 
branches. Thorns, which are really modified leaves, are 
very perfectly exemplified in the barberry (Fig. 88). It 
is much commoner to find the leaf extending its midrib or 
its veins out into spiny points, as the thistle does, or bear- 
ing spines or prickles on 
its midrib, as is the case 
with the nightshade 
shown in Fig. 89, and 
with so many roses. 
Stipules are not infre- 
quently found occurring 
4! 
Y ‘ 
WOON Bye, 89. Leaf of a mon locust (Fig. 91) the 
_ Nightshade (Solanum bud, or the very young 
\ ACUI) shoot which proceeds from 
it, is admirably protected by the jutting thorn on either side. 
145. Pointed, Barbed, and Stinging Hairs. — Needle- 
pointed hairs are an efficient defensive weapon of many 
plants. Sometimes these hairs are roughened, like those 
of the bugloss (Fig. 92, 4); sometimes they are decidedly 
barbed. If the barbs are well developed, they may cause 
the hairs to travel far into the flesh of animals and cause 
intense pain. In the nettle (Fig. 92, a) the hairs are 
efficient stings, with a brittle tip, which on breaking off 
exposes a sharp, jagged tube full of irritating fluid. These 
tubular hairs, with their poisonous contents, will be found 
sticking in the skin of the hand or the face after incau- 
tious contact with nettles, and the violent itching which 
follows is only too familiar to most people. 
as thorns, and in our com- 
