10 HABITS OF AVOIUIS. CHAP. I. 



burrowed through the floor of a very damp 

 cellar. I have seen worms in black peat in a 

 boggy field ; but they are extremely rare, or 

 quite absent in the drier, brown, fibrous peat, 

 which is so much valued by gardeners. On 

 dry, sandy or gravelly tracks, where heath 

 with some gorse, ferns, coarse grass, moss and 

 lichens alone grow, hardly any worms can 

 be found. But in many parts of England, 

 wherever a path crosses a heath, its surface 

 becomes covered with a fine short sward. 

 Whether this change of vegetation is due to 

 the taller plants being killed by the occasional 

 trampling of man and animals, or to the soil 

 being occasionally manured by the droppings 

 from animals, I do not know.* On such 

 grassy paths worm-castings may often be seen. 

 On a heath in Surrey, which was carefully 

 examined, there were only a few castings on 

 these paths, where they were much inclined ; 



* There is even some reason to believe that pressure is actually 

 favourable to the growth of grasses, for Professor Buckman, who 

 made many observations on their growth in the experimental, 

 gardens of the Royal Agricultural College, remarks (' Gardeners' 

 Chronicle,' 1854, p. 619) : " Another circumstance in the cultiva- 

 tion of grasses in the separate form or small patches, is the 

 impossibility of rolling or treading them firmly, without which 

 no pasture can continue good." 



