97H 



against 31.35 of CaO. With reference to this it is obvious that tiie 

 phosphate engendered contained cliieflj only Ca, while from the ash 

 anaij'sis the conclusion might be drawn that one tree absorbs more 

 Mg than the other. 



1 think it is in keeping witlj the general rule to state that the 

 concretions have originally been made up of calcinmphosphate, which 

 afterwards was gradually changed under the influence of a detached 

 organic magnesiumsalt. This change caused the formation of magne- 

 siumphospiiate, which is more difficult to dissolve ') .The clear crystal 

 grains could tlien be looked upon as the still untouched lemainder 

 of the calcinmphosphate. Without such a metamorphosis the two phos- 

 phates must have been secreted simultaneously, which does not seem 

 probable to me. Still less can theie be any question of periodicity 

 in the secretion of the two phosphates, because this would have to be 

 proved by a zonary structure, which could not l)e detected in any 

 of the preparations. To solve the question we need a larger amount 

 of material. I also deem it necessary to analyse, besides the con- 

 cretions themselves, also the wood of the stems from which they 

 originate. 



Tectonn grandis is the greatest phos|)horus devourer known, it 

 would, therefoie, be interesting to find ont whether on that account 

 it also spoils the soil '). The amount of phosphoric acid it absorl)S, 

 may be computed from the annual amount of djati wood, cut in 

 Java. From 1902 to 1915 (inclusive) it was 



3.148950 M.' of timber and 

 J 1.035108 M.' of firewood'), 

 representing respectively a weight of 2074.347000 kg. ■*) and 

 4855.447740 kg. '). 



According to Romanis heartwood yields 1 7o a"<l sapwood 0.74 "/^ 



1) I do not think it at all improbable thai sucli a change can be ciïecled experi- 

 mentally, viz. through impregnation of squashed cell-sap of Mg-rich teak-treee into 

 normal concretions of calciumphosphate. 



2) The question whether djati is a spoiler of the ground has given rise to some 

 controversy, however, only with respect to the slight formation of humus in the 

 forests. (J. C Claesen, lets over djati. Boschbouwkundig Tijdschr. Tectona 1. 

 Noordwijk- Weltevreden 1908—9, p. 166. — H. J. Kerbert, Is djati grondbe- 

 derfster? Ibid. 1. 1908—9, p. 301— 304; 2. 1909 — 10, p. 44— 46. — J. G. Claesen. 

 Antwoord aan den heer Kerbert. Ibid. 1, p. 575). 



^) Verslag van den Dienst van het Boscliwezen in Nederl.-lndië over het jaar 

 1915. Batavia 1916, p. 18. 



*) The average specific weight was fixed at 0,66. 



*) Firewood is calculated by the running meter. It consists of branches and 

 other debris of wood, leaving empty spaces that were subtracted as ^'3. 



