83 



under the microscope showed an abundance of cells fiUcd with this dark-coloured 

 substance ; a strong reaction for manganese was obtained with the ash of the timber 

 of this tree, and it was even more pronounced than that given with C. glauca. 



. Although the fusion 

 presence of manganese, yet, 

 woods, so that the far more 

 delicate test of boiling the 

 ash with nitric acid and 

 peroxide of lead was 

 adopted ; this method was 

 also made of quantitative 

 value. The process was 

 carried out as follows: — 

 0-03 gram of the freshly 

 ignited ash was boiled in a 

 test tube with 2 c.c. nitric 

 acid, 0-5 gram lead per- 

 oxide, and 6 c.c. water, 

 until the volume had been 

 reduced about one fourth ; 

 it was then stood on one 

 side for some time. The 

 colour of the clear solution 

 in the test tube was then 

 matched by diluting a 

 solution of potassium per- 

 manganate, I gram per 

 litre, until the required tint 

 test tubes of equal diameter. 



test was sufiicient in most cases to determine the 

 , it was hardly distinctive enough with the lighter 



Transverse section at junction of inner and outer cortex, showing the 

 dark brown substance or manganese compound in the parenchy- 

 matous cells. C. arcnosa, x loo. (See also coloured plate, Figure 

 105.) 



was obtained ; the two solutions were compared in 



With 0-03 gram of the ash of C. intratropica it was only necessary to dilute 

 I c.c. of the potassium permanganate solution ten times to obtain the corre:sponding 

 tint, the wood of this tree, as before mentioned, being quite dark coloured. With 

 the ash of C. verrucosa (a very light wood) it was necessary to dilute i c.c. seventy 

 times before the tints agreed in depth of colour. The timber of C. glauca gave an 

 ash which, when tested as above, required the standard permanganate solution 

 to be diluted twenty times, while the same amount of the ash of C. calcarata 

 required it to be diluted seventy times ; and so on throughout the whole range of 

 timbers of this group, the darker woods showing the presence of more manganese 

 than the lighter woods. 



To test the quantitative value of this method the amount of ash taken 

 was often doubled for the duplicate test, and the results thus obtained were 



