HOW PLANTS PROTECT THEMSELVES 351 
420. Weapons of Desert Plants. — In temperate regions, 
where vegetation is usually abundant, such moderate 
means of protection as have just been described are gener- 
ally sufficient to insure the safety of the plants which have 
developed them. But in desert or semi-desert regions the 
Fic. 247. — Stinging Hairs and Cutting Leaves. (All much magnified.) 
a, stinging hairs on leaf of nettle; 5, bristle of the bugloss ; c, barbed margin 
of a leaf of sedge ; d, barbed margin of a leaf of grass. 
extreme scarcity of plant life exposes the few plants that 
occur there to the attacks of all the herbivorous animals 
that may encounter them. Accordingly, great numbers of 
desert plants are characterized by nauseating or poisonous 
qualities or by the presence of astonishingly developed 
thorns, while some combine both of these means of defense. 
