^o THE BOOK OF NATURE STUDY 



Sometimes plants which belong distinctly to the lowland are 

 found in Alpine pastures, in sheltered spots under the lee of rocks. 

 Those who are within reach of the fells in the Lake district 

 might keep records of the lowland plants found above 2000 feet. 

 The following list is given by Mr. Lewis. 



Adoxa at 2480 feet. 



Wood Sorrel . .'-'.'. . . . ,, 2500 ,, 



Herb Robert ,, 2300 



Water Avens 2250 ,, 



Wild Angelica ... . 2100 



Slender St. John's Wort . . . 2200 



THE DRAINAGE OF GRASSLAND. The level of the ground 

 water is of great importance to plants. By ground water is 

 meant the layer of water situated above some impermeable layer ; 

 for instance, a sandy or gravelly pasture may be situated on a 

 geological layer of clay, there will be a layer of ground water 

 between the pasture and the clay. The level of this ground 

 water varies with the nature of the soil, and to some extent with 

 the season, and it is found that vegetation varies with the level 

 of the ground water. Warming quotes Feilberg's observations 

 on the sandy plains near Skagen in Jutland. When the ground 

 water in summer is at a depth of three inches, Juncus vegetation 

 and meadow-moor prevail ; at six inches Mosses and Sedges are 

 dominant, but Grasses begin to occur ; at nine inches these are 

 dominant ; cereals thrive when the water is at a depth of from 

 eighteen to twenty-four inches ; at from thirty to forty, Xerophytes 

 reign. 



Drainage is essential for several reasons. If soil is water-logged 

 the roots are confined to the surface layer ; they cannot penetrate, 

 for they must have air, and if the spaces between the particles 

 of soil are filled with water they cannot be filled with air. The 

 following experiment shows how much air dry soil may contain. 

 Estimate the volume of a glass vessel by noting how many cubic 

 centimetres of water are necessary to fill it. Dry the vessel 

 thoroughly, and fill it with soil which has been thoroughly dried 

 in the sun or in an oven. Then pour water into it, noting how 



