Avoid Excess 



of phosphates is often recognisable by a purphsh 

 tinge in the foliage of grasses, especially of barley 

 and the like. 



An excess of nitrogen leads to a lush, sappy 

 growth which falls ready victim to fungi and is much 

 more hable to damage by frost than more sturdy 

 tissue. Such growth is characterised by a deep 

 green colour, large watery foHage, and often long 

 intemodes, which are not, however, thin. It often 

 follows the too liberal use of organic manures or 

 nitrate of soda and sulphate of ammonia. Soils 

 which grow chickweed and fat-hen (goose-foot, 

 Ghenopodium album) vigorously are usually suffi- 

 ciently supphed with nitrogen. 



Excess of Ume is characterised by yellowing of the 

 foUage, which may be of rather small size, and may 

 be entirely or only partially devoid of green colouring 

 matter. The growth is usually sturdy and the 

 intemodes short. The lack of green colour of course 

 checks food-making more or less completely, and the 

 result is disastrous to the plant. It may be cured 

 by the apphcation of sulphate of iron to the soil at 

 the rate of 2 oz. or so to the square yard. Roses 

 and laurels frequently show this disease, which is 

 termed chlorosis, when growing iu chalky soils. 



A curious cause of infertihty, not marked by any 

 very characteristic symptom in the plants except 

 general tardiness in growth, is found when the 

 amount of magnesia present is in excess of that of 



33 D 



