HOW LEAVES PROTECT THEMSELVES 



91 



10. Hairs are often so thick 

 or so stiff that they help to 

 keep off animals. In a few 

 cases, too, the hairs sting, as 

 in the nettle. The soft noses 

 of cattle are easily hurt. Look 

 through a lens at a nettle-hair. 

 It consists of a tiny flask of 

 stinging fluid, and this flask 

 ends in a very delicate sharp 

 point. If you snip off a little 

 piece of leaf or stem with a 

 pair of scissors, and hold it 

 on a pin, you can look at 



Fig. 69.-The Common rib- the " sting " COmfortably. 

 grass, which lies flat when 

 there is danger of being 

 cropped. 



Questions and Exercises. — 



(1) Find out how the wood-sorrel protects its 3 leaflets from tho 

 night cold. 



(2) How do the opening leaves of the following plants guard 

 against cold? Periwinkle, common garden pea, castor-oil plant, 

 ferns. 



(3) Fires of damp bushes causing much smoke are sometimes lit 

 in orchards in spring to keep off frost. Explain. 



(4) One sometimes sees in spring a light covering of straw on 

 potato plants. How does this help the plants ? 



(5) Name any plants in your district that stand drought well, 

 giving reasons. 



(6) The leaves of the holly near the ground have prickles, but 

 those higher up have none. Explain. 



(7) The shining dots that you see in a gum tree leaf when the 

 leaf is held up to the light are scent-cells. Can you tell of any 

 way in which this scent may be of use to the leaves ? Name any 

 other plants in your district that have scented leaves. 



(8) Study the summer weed called wire- weed, and find out why 

 it can grow on bare, dry patches where little else can grow. If 

 possible, take up the whole root. 



