314 REPoRT OF THE BOTANICAL DEPARTMENT OF THE 
beneath, but it remains to be shown that such arsenic, though 
it may become soluble in soils, injures or kills the trees. 
Neither the association of a wounded tree and some fungus 
nor an injured tree and arsenic are certain indications that 
either the fungus or arsenic has any causal relation to the 
injury of the tree. 
Headden has shown by a number of analyses that consid- 
erable quantities of arsenic are present in the soil under some 
sprayed fruit trees, that crown-injured trees contain arsenic, 
that lead arsenate is appreciably soluble in dilute salt solu- 
tions, that lime arsenite goes into solution in the presence of 
sulphate of lime and that potted herbaceous plants died after 
the application of from .05 to .5 gram, of “ sodic arsenite.’ But 
he has failed to show that arsenic is not present in uninjured, 
sprayed fruit-trees, whether the arsenic in the soil and trees 
is present as arsenates or arsenites, that arsenates or even 
arsenites are poisonous to fruit-trees when absorbed by their 
roots, if poisonous what amounts become injurious, how poison 
absorbed by tree roots can discolor or injure the heart-wood 
before discoloring the alburnum and cortex, and whether the 
arsenic was absorbed through the bark of the roots near the 
trunk or through the usual channels (root hairs) at the pe- 
riphery of the root system, some distance from the trunk. 
It cannot be taken for granted that the arsenic is present in 
the soil as an arsenite, nor that an arsenate is poisonous to 
fruit trees, for Pfeffer®® says “ Arsenious acid is extremely 
poisonous, whereas many, both of the higher and of the lower 
plants, can withstand large doses of arsenic acid and can 
accumulate large quantities of arsenic when supplied to them 
in this form,” while F. Czapek*! says that traces of arsenic 
are nearly always present in soils and may therefore be ab- 
sorbed by plant roots. Though it has been shown by Nobbe, 
Baessler and Will*? that some herbaceous plants and some 
* Pfeffer’s Physiology of Plants, 2nd revised ed., translated by A. J. 
Ewart, Vol. I, p. 438. 
* Biochemie der Pflanzen. Vol. II, pp. 862-63. 1905. 
* Untersuchung iiber die Giftwirkung des Arsens, Blei und Zink im 
pflanzlichen Organismus. Landw. Vers. Stat., 30: 381-423. 1884. 
