146 PLANT LIFE. 



blows on the under surfaces of the leaves, whose stalks 

 have a sort of conical shape, each being at a very acute 

 angle to the stem ; each leaflet also twists, so as to get 

 nearly as possible edgewise. Everything, branch, leaf- 

 stalk and leaflet, sways to and fro, thus enormously 

 diminishing the force of the air on the leaves. 



In the Beech the natural position of the branches and 

 leaves is nearly horizontal ; the leaf is rather tough in 

 texture, and is well strengthened by supporting veins; 

 and the branch strives to keep the leaves edgewise to 

 the wind, and does not bend like the ash. 



It is very possible that many cases of much divided 

 leaves, such as the Horse-chestnut, Geraniums, Umbelliferae, 

 Leguminosae, Rosaceae, etc., can be explained by this 

 necessity of supporting the wind. In many plants, 

 however, the fine divisions of the leaf are intended to 

 enable the leaves to be neatly packed away in the bud 

 condition. This is very nicely seen in the Bishop's Weed 

 and other plants of the same order, as well as in the 

 Tansy (see Fig. 7, p. 68). At present there are un- 

 fortunately very few exact open-air observations which 

 can be referred to in support of the explanation of leaf 

 division here given. 



In Poplars, the leaf stalk is very long and very 

 flexible. It is quite different in shape from that of most 

 other leaves, being compressed or flattened vertically 

 near the blade ; one of these poplar leaf stalks can be 

 twisted round into two or three close spiral turns or 

 corkscrew coils, without being in the least injured ; the 

 leaf can therefore very easily arrange itself edgewise to 

 the wind and will not easily be torn away. It is, how- 

 ever, the elasticity or flexibility of plants generally that 

 is their main protection against storms. It is very 

 interesting to watch grasses and reeds in heavy winds. 



