96 THE FACTORS [Part I 



from that which it exhibits on calcareous soils upon which it usually 

 grows. 



In order to ascertain whether this distinction was due to the influence 

 of calcium, comparative cultural experiments were undertaken by Bonnier, 

 in which seeds from one and the same parent were employed, and sown on 

 soil poor in lime (4 sand, i clay) and on soil rich in lime (§ calcium 

 carbonate, i sand). The resulting plants differed in appearance according 

 to the nature of the substratum. On the soil rich in lime they formed 

 taller and less spreading tufts, broader leaves, shorter sepals, and possessed 

 a colour different from that of those on the soil that was poor in lime. Even 

 histological differences also were observed. The plants that were poor 

 in calcium possessed a lignified pith, numerous fibres, and thick palisade- 

 tissue in their leaflets, whereas those grown on calcareous soil produced 

 an unlignified pith, less numerous fibres, and looser palisade-tissue. 



Numerous observations in the field, especially those by Fliche and 

 Grandeau, have also demonstrated a distinct action of calcium on the 

 structure of plants. 



These observers have recorded that Robinia Pseud-acacia, which is a plant in- 

 different as regards the chemical constitution of the soil, as it grew in the forest of 

 Champfetu, exhibited the following variations according as it grew on soil that was 

 rich or poor in lime : the wood on soil poor in lime assumes a brown colour after 

 the seventh year, but on calcareous soil not until after the ninth year. The bark 

 is thinner and denser in the former case, the sap-wood bright brown, whilst on 

 calcareous soil it is yellow, and the vessels are more numerous and wider. In wood- 

 parenchyma, starch is more abundant on soils poor in lime, albuminates more 

 abundant on the calcareous soil. The pods are longer and much broader in the 

 former case, and more lightly coloured than on calcareous soil. 



Masclef examined specimens of Pteris aquilina which were grown side by side on 

 calcareous and clay soils. In the former case, the rhizomes were shorter, provided 

 with more numerous and thicker roots, the reserve parenchyma was more feebly 

 and the protective tissues more strongly developed. 



Timbal-Lagrave and Malinvaud discovered that Asclepias Vincetoxicum is repre- 

 sented by different races on calcareous soil and on soil poor in lime. 



Hilgard has made extensive observations in North America on the influence 

 of calcium on the configuration of plants. Quercus ferruginea and Q. obtusifolia are 

 stunted on sand and on black prairie soil, but tall and with a different ramification 

 on calcareous soil. According to Hilgard, an increase of the lime in soils increases 

 the yield of many economic plants, especially of cotton. 



There are, up to the present time, only a few observations available as 

 to the nature of the influence of calcium carbonate on plant-metabolism. 

 Yet the critically conducted and extensive researches of Fliche and 

 Grandeau l have made the first substantial advance in the desired 

 direction. 



1 Fliche et Grandeau, I, II, III. 



