Botany. 459 
Silica 10.300 per cent. 
Ferric oxide 2.100 per cent. 
Alumin 2.600 per cent 
Oxide of manganese 1.672 per cent. 
Lime 12.700 per cent. 
Magnesia : 11.351 per cent. 
Potassa 12.759 per cent. 
Soda... 14.856 per cent 
Sulphuric acid 7.419 per cent. 
Chlorine 6.947 per cent.. 
Carbonie acid 12.900 per cent. 
Phosphorie acid + 93.034 per cent. 
99.638 
But one other analysis of this ash has been found by me;. that 
of Avequin,' in 1835, which is recorded in the following way (in 
effect, as I have not the exact language at hand) :— 
Osten grammes of dry plant gave 32.35 grammes of ash, composed 
Salts of potash (phosphate, sulphate, carbonate 
ande ide) 
: ) 11.47 gr. 
Lime (partly as carbonate) 5.96 gr. 
Phosphates of lime and magnesia 9.26 gr. 
Silica containing a little iron and manganese...... 5.66 gr. 
32.35 
It will be observed that the total ash (3.235 per cent.) is nearly 
the same as that obtained by me. If the iron and alumina, as well 
as the manganese, in my analysis, are added to the silica, the sum 
1s 16.672 per cent., which is not greatly different from the impure 
silica of Avequin, 17.186 per cent. It would therefore appear that 
the plant must uniformly have some such ash as that found above. 
(Indeed, the ash of any one plant, as is well known does not vary 
greatly.) What, then, shall we think? That the roots do absorb 
the characteristic ash-constituents from the trees on which they 
grow? That would seem to me more rational than to suppose 
them to be absorbed from the floating matter of the air. But if 
we do arrive at this conclusion, our idea of the term epiphyte must 
certainly undergo a radical change—T, Chalkley Palmer. 
Tue Errecr on VEGETATION OF THE VARIABLE RAIN- 
FALL OF NORTHWESTERN Mexico.2—First, want of water. 
Those who have travelled over the northwestern portion of Mexico 
Will, I think, agree with the writer that it is a dry, barren section, and 
in want of water. Rains are very uncertain, often years passing 
Without a shower sufficient to cause a good growth of vegetation. 
When the first white settlers made their homes in this region, over 
two hundred years ago, they did so during a very dry period of 
several months, during which they formed the conclusion that th 
* Journal de i : 
sn, Read before the Botanical section of the Biological Society of Wash- 
ington, March 7, 1888, 
