ASH. I 



79 



numberless analyses we learn that such accumulations take place in individual 

 plants specifically differently, and further, that different species may grow in the 

 same situation and yet show quite different ash constituents. As an example 

 we may take the analysis which Grandeau and Bouton (1877) have made of 

 the mistletoe, and of the different media from which it obtains its ash : — 



This table clearly shows that the mistletoe has markedly less silicic acid, 

 less lime, and much more potash and phosphoric acid than its host. Moreover, 

 the plants growing on these three different substrata are by no means similar in 

 chemical composition, and the differences between them cannot be in any way 

 referred to corresponding differences in the substrata. These differences are 

 peculiar to the individual and are at present inexplicable. It is self-apparent 

 that a definite species can, caeteris paribus, take up more of a substance from 

 a soil which contains it abundantly than from one which contains little, as is 

 shown by Malaguti and Durocher's (1858) work on the analysis of lime as 

 a constituent of plant ash. 



The total amount of ash in the example given above is very limited and 

 constitutes only a small percentage of the dry weight, but in other cases, the 

 amount is quite considerable. In addition to the large table given below, the 

 first column of which shows this fact prominently, we may extract the following 

 figures from Wolff's ' Ash Analysis ' (I, 137), dealing with several common 

 weeds grown on similar soils. The ash of Rumex acetosella amounted to 

 8'i4 per cent., of Geranium dissectum to 9-98 per cent., of Sedum telephium to 

 11-96 per cent., and Myosotis arvensis to 17-85 per cent, of the dry weight in 

 each case. Far larger quantities of ash are found in seashore plants ; e. g. 

 16-51 per cent, in Aster tripolium, 17-91 per cent, in Artemisia maritima, 

 and 31-57 per cent, in Chenopodium maritimum. Although we must attribute 

 the large proportion of ash in these cases to the presence of large amounts of 

 common salt in the sand, still we find other conditions in other cases tending to 

 increase the amount of ash constituents. We need refer here only to transpira- 

 tion. On grounds which are easily understood, plants which transpire freely 

 are far richer in ash than those which transpire feebly, and the leaves, being the 

 organs of transpiration, appear to contain most. On that account transpiration 

 is of great value to the plant, because, as we shall see presently, the constituents 

 of the ash are essential to its well-being, and by no means superfluous or injurious. 



The individual elements which occur regularly in the ash of all plants are only 

 eleven in number, i. e. : — chlorine, sulphur, phosphorus, silicon, and the metals 

 potassium, sodium, calcium, magnesium, iron, aluminium, and manganese. 

 As a rule the last two occur as traces only, the rest abundantly. The following 

 table (Wolff, 1880) shows the composition of the ash of certain plants, but only 

 the nine principal elements are noted ; the special abundance of an element is 

 emphasized by italics. 



