LIFE HISTORIES OF FAMILIAR PLANTS 



competition for sunlight is small, we find the 

 leaves large and broad. Water-lilies present a 

 striking instance (Fig. 115, Plate 83). In the 

 middle of the open river there is ample room, 

 and consequently the leaves of the water-lilies 

 can spread out freely to the air and sunlight, and 

 so they become large and almost circular ; but in 

 crowded places such as pastures and thickets, 

 where the competition for light and air is keen, 

 the leaves are usually much divided, as in butter- 

 cups and in the wild camomile already discussed. 



Therefore the broad leaves of the coltsfoot are 

 the best suited and most economical for the bare 

 railway cuttings and the poor soils favoured by the 

 plant. Note, too, how the under side of each leaf 

 is felted with a thick covering of woolly hairs. By 

 the river bank and in the clay valleys, where the 

 coltsfoot is so often found, the leaves are much 

 subjected to mist and vapour from the heavy dews 

 of night and morning, and it is on the under side 

 of them that the tiny '' breathing-pores," through 

 which the plant effects its interchange of gases 

 with the atmosphere, are found. The leaves could 

 not carry on their functions of starch manu- 

 facture if these tiny pores were allowed to get 

 clogged ; so it happens that a thick felting of hairs 

 protects their lower surface, and this throws oft 

 water like the proverbial duck's back. Such leaves 

 are common to plants that grow in moist quarters ; 

 some willows, alders, thistles, and the common 

 meadow-sweet exhibit a like feature. 



Such, then, is a brief outline of the curious 



116 



