THE STONECROPS 



summer season, when vegetable food is abundant, 

 vegetable-feeding animals would scarcely trouble 

 to climb difficult rocks and heights in search of 

 them. 



Hence, the stonecrops have had a very un- 

 eventful career, going their way more or less 

 unmolested ; even the ground they occupy is 

 easily held, for few British plants can tolerate a 

 stony soil and a scorching sun. 



Consequently, we find that the structure of 

 these plants is very simple. The leaves, in the 

 larger species, are more or less round, like large 

 fleshy scales. Competition for sunlight has not 

 necessitated that they should assume lobed or 

 deeply divided forms, like the plants of the 

 meadows, hedgerows, and woodlands, where the 

 struggle for light and air is ever keen and con- 

 stant. Hence they have retained, more or less, 

 their primitive shapes. In the smaller species, as 

 in the wall-pepper, the little leaves have become 

 closely arranged against their stems, for in this 

 manner their smaller amount of retained moisture 

 is better protected from the heat of the sun's rays 

 and its evaporation retarded. 



Turning to the flowers we find still greater 

 evidence of the primitive simplicity of these plants. 

 At some remote period in plant evolution, a great 

 division into two distinct groups seems to have 

 taken place (although why and how this division 

 came about is one of the unsolved problems of 

 science). One group proceeded to develop the 

 whorls of its flowers in fives ; i.e.j five or ten 



163 



