304 SOIL CONDITIONS AND PLANT GROWTH 



where the calcium carbonate exceeds about 10 per cent, and 

 dominates every other constituent, becoming the controlling 

 factor in determining the soil properties. The conditions 

 here seem to be extraordinarily well suited to plant and animal 

 life. Bacteria are numerous and active, rapidly oxidising 

 organic matter. Hosts of animals, wireworms, earthworms, 

 and others live in the grass land, and even get into the arable 

 land, honeycombing the soil with their passages, purring it 

 up or " lightening " it considerably, and encouraging the 

 multiplication of moles. Rabbits abound in dry places. 

 Vegetation is restricted on thin exposed soils, but becomes 

 astonishingly varied where there is sufficient depth of soil and 

 shelter to maintain an adequate water supply. Ash is the 

 characteristic tree in the north and west, and beech in the 

 south of England, and there is a great profusion of shrubs 

 buck thorn, spindle, guelder rose, dogwood, hawthorn, hazel, 

 maple ; and especially of flowering plants scabious (S. Colum- 

 baria], the bedstraws, vetches, ragwort, yellow wort (Chlora 

 perfoliatd), salad burnet (Poterium sanguisorbd], lady's fingers 

 (Anthyllis), Linum cartharticum, Bromus erectus. Still more 

 remarkable, perhaps, is the fact that a few plants the so- 

 called calcifuges do not occur. Where the amount of calcium 

 carbonate is too high plants tend to become chlorotic ; 

 Chauzit showed that vines suffered badly when 35 per cent, 

 or more was present, but not when the amounts fell to 3 per 

 cent 1 Maze (197) attributes part of the action to the render- 

 ing insoluble of zinc, manganese, etc., necessary for complete 

 growth (p. 56). 



Investigations in Porto Rico (105), where a considerable 

 portion of the arable land is sufficiently calcareous to produce 

 nutritional disturbances in crops, show that bush beans {Phase- 

 olus nanus] and radishes are unaffected by even 35 per cent, of 

 CaCO 3 ; sunflowers, soy beans, and sugar canes are somewhat 

 depressed ; while sweet cassava (Manihot palmatd), rice and 

 pine-apples were considerably depressed by this amount. The 



1 See Revue de Viticulture, 1902, xviii., 15, and also Molz, Centr. Bakt. Par., 

 Abt. ii., 1907, xix., 475. 



