ABSORPTION OF ASH-COXSTITUENTS 



8 9 



This distribution of the ash shows that the tissues richest in ash are those 

 in which living cells are most numerous, such as those of algae and the leaves 

 and cortex of the beeech. Dead cells contain much less ash, since the salts 

 begin to pass out at about the time death occurs; thus, the hard wood of 

 the beech contains much less than does the dry substance of the living leaf 

 tissue. 



Different amounts of ash occur in different organs of the same plant. Leaves 

 are richer in ash than stems and roots. The amounts of the different chemical 

 elements likewise vary; calcium, for instance, predominates in leaves. 



The ash content of each organ changes during the course of its development; 

 in leaves it increases with age, while in roots and stems it decreases. In the 

 case of roots and stems the number of dead cells, poor in ash, increases with age. 

 The following table gives the total ash content and the proportions of the vari- 

 ous elements in the ash, for beech leaves {Fagns sylvatica) at three different 

 stages of their development. 



Date 



May 16 

 July 18 

 Oct. 15. 



Total Ash, 

 Per Cent, of 

 Dry Weight 



4-i 

 4-7 

 7-i 



Amounts of Various Elements in Ash, Cal- 

 culated as Oxides, Per Cent, of Total Ash 



K 2 CaO MgO Fe 2 3 P 2 5 SiO 



42.1 

 17. 1 



7.1 



138 



42.3 

 50.6 



4-3 

 5-6 

 4-1 



0.8 

 i-4 

 1-3 



32.4 

 8.2 



5-i 



1.6 

 21.3 

 30.5 



These analyses of beech leaves show how strikingly the amount of the differ- 

 ent ash-constituents alter with the age of the leaves. Calcium and silicon show 

 a marked increase in amount while potassium and phosphorus decrease as the 

 leaves become older. But, as has been well pointed out by Wehmer, 1 it is not 

 to be concluded from these analyses that the absolute amounts of potassium 

 and phosphoric acid diminish in such leaves. For example, if 50 g. of potassium 

 and 50 g. of other elements were present in a certain quantity of young leaves, 

 we should then find 50 per cent, of potassium in the ash. If we suppose that 

 the leaves take up 100 g. more of the other elements but that the amount of 

 potassium remains unchanged, then we should expect to find only 25 per cent, 

 of potassium in the ash of the older leaves. According to Riesmiiller's anal- 

 yses, the ash of 1000 beech leaves contained, at different times of the year, 

 the percentages and absolute amounts of potassium shown in the following 

 table. 



1 Wehmer, C, Zur Frage nach der Entleerung absterbender Organe, insbesondere der Laubblatter. 

 Unter Berüchsichtigung der vorliegenden Aschenanalysen vom kritischen Standpunkte beleuchtet. 

 Landw. Jahrb. 21 : 513-560. 1892. 



