WOOD SORREL 131 



If you examine a leaf -bud of wood sorrel, you will find 

 that each leaflet is doubled in two, and all three are laid 

 side by side (Fig. 33). This is exactly like the folding in a 

 clover-bud. See how densely the buds are clothed with 

 hairs ; I suppose for protection in the bleak spring weather. 



The slender prostrate stem spreads over the leaf-mould, 

 sending down its roots into the earth here and there. 

 Wherever a number of leaves spring from the stem, it 

 becomes enlarged, and every such enlargement is capable, 

 if detached, of subsisting as an independent plant. 



The leaves of wood sorrel are distinctly acid, and the 

 acid is oxalic acid combined with potash. There is much 

 in the leaflets, still more in the leaf-stalks, very little in 

 the enlarged leaf-bases. Is the acid a mere waste-product, 

 or has it a defensive function ? Wood sorrel is not often 

 bitten by insects ; Stahl found that snails do not eat it, 

 and that the leaves of favourite plants, when washed in a 

 one per cent, solution of potash oxalate, are refused even 

 by famishing snails. 



Though the shape of the leaves of clover and wood 

 sorrel is so similar, it is probable that they originated in 

 different ways. This seems to be shown by the leaves 

 which are borne by their nearest relations. Clover belongs 

 to the great family of leguminous or pod- bearing plants ; 

 wood sorrel is a peculiar sort of geranium. Now legumin- 

 ous plants have often pinnate leaves, composed of several 

 pairs of leaflets, with an odd one at the tip. If we suppose 

 the numerous pairs of leaflets which we find in most vetches 

 reduced to a single pair, these, together with the odd leaflet, 

 would make a trefoil, such as that of clover ? How can 

 we tell which is the original odd leaflet in the trefoil leaf 

 of clover? It is that one whose stalk, when extended, is 

 in line with the main leaf-stalk, and which overarches 

 the other two when the leaf goes to sleep. 



Geraniums do not usually bear pinnate leaves, but their 

 rounded leaves are often deeply cut, and in one English 

 geranium (dissectum), each is cleft into three parts, not 



