20 JOURNAL OF THE ROYAL HORTK ULTURAT, SOCII^VrY. 



contain only a small proportion of carbonate of ]inie. Anyone 

 botanizing in the South of England will have noticed how strictly 

 certain shrubs like the wayfaring tree, the dog-wood, the wild Clematis, 

 and flowering-plants like Hip'pocrepis and some of the orchids are 

 confined to chalk and limestone districts; he caimot doubt that these 

 plants do in some way depend upon the rid mess of their soil in 

 carbonate of lime. Among the leguminous plants we find some of the 

 most remarkable associations of particular species with calcareous soils. 

 Some species, like the Hippocrepis we have mentioned, never occur 

 elsewhere, while most of the cultivated species, particularly sainfoin 

 and the clovers, are most at home on a calcareous soil. There are, 

 however, others, like some of the species of Lathyrus and Vicia, lupins 

 and serradella, which are typical sand-loving plants and seem to avoid 

 the calcareous soils. Here would seem tO' be a case of aissociation tliat 

 lends itself to experiment, yet as soon as such plants are placed vmder 

 pot or trial plot conditions they seem indifferent to the amount of 

 carbonate of lime in the soil. A year or two ago I selected some of 

 these typical non-calcareous leguminous plants and had them grown 

 at Woburn on a sand that contained practically no carbonate of lime, 

 and at Eothamsted in a soil that was well limed at the outset. Both 

 sets of plants grew well, and when an analysis was made of their ashes, 

 as Table YIII. shows, they contained very similar amounts of lime, 

 from whichever soil the plant had been derived. 



Table VIII. 



Percentage of Lime in Ash of Leguminous Plants 



Species 



Woburn (no CaOOg 

 in soil) 



Eothamsted 

 (0-6 per cent. OaCo., in soil) 





19-0 



26-9 



Ornithopus sativus 



27-1 



20-7 



Lupinus albus .... 



18-3 



15-9 



L. varius var. angustifolius . 



36-1 



38-3 



L. luteus ..... 



■ 30-6 



31-9 



Vicia fulgens .... 



23-9 



27-6 



Lathyrus Cicera .... 



18-3 



15-6 



Other successes have been reported when attempting to grow 

 presumably lime-hating plants in calcareous soils, and one can only 

 suppose that carbonate of lime does not inhibit plants like lupins, 

 but on the other hand it favours the plants like Hippocrepis. It 

 is a positive and not a negative factor. The experiments fail because 

 we cannot introduce the element of competition in order to deter- 

 mine how much greater the vitahty of the plant is in one case than 

 the other. Under experimental conditions both sets of plants are 

 relieved from competition and grow up to the maximum of their food 

 and water supply, though the vitality of one may be so much the less 

 that it would succumb under any stress of competition. We have, 

 indeed, to bear in mind that the vigour which a plant can show, for 

 example, by the amount of growth it makes, is little or no index to 

 vitality. 



