ArsenicaIv Poisoning oe Fruit Trees. 25 
still further. It is stated on ,good authority that marly soils are 
unfriendly to a number of plants. Many of our soils are rich in car¬ 
bonate of lime and others are underlaid by a stratum of marl, car¬ 
bonate of lime, sometimes acquiring- a thickness of two feet or more. 
It is a serious question in my mind whether this is not a bad 
feature. My attitude toward this subject is exactly the same as that 
toward the one or arsenical poisoning, i. e., that the subject should 
not be mentioned without good and forcible reasons for doing so. 
Why mention this then at all ? 
I have called attention to the fact that many trees, evidently in 
an unhealthy condition, are bleeding freely from old wounds, stubs, 
where limbs and branches have been cut off and from cracks in the 
bark (Plate V., Figs, i and 2). This sap is heavily laden witli 
salts of some kind, dries quickly, and deposits a yellowish white 
crystalline mass. This mass when fresh possesses, at least some¬ 
times, a disagreeable taste; the thoroughly dried salt has not a par¬ 
ticularly unpleasant one. I have seen this juice dripping from a 
crack in the bark and building a veritable stalactite of this material 
Mr. Weldon, our Field Entomologist, and I gathered a quantity 
of this material, avoiding as far as possible the scraping of the bark, 
lest we should get some of the spray material. The conditions ex¬ 
posed our sample to contamination in this manner and by dust, 
which might contain arsenic, being blown into it, but I think that 
the results obtained from this sample may be accepted as, in the 
main, reliable. This material was very rich in arsenic and contained 
25 per cent of calcic oxid. I do not believe that the splitting or 
cracking of the bark and the bleeding are specific characteristics of 
arsenical poisoning but are attributable to other causes which in these 
‘cases may act conjointly with the arsenic. The destruction of the 
bark by the arsenic is an entirely different thing from this cracking 
or splitting of the bark. 
Having found that this dried sap was an interesting subject, 
we gathered a second sample. The preceding sample was gathered 
before the first spraying of the season had been made, but the sec¬ 
ond was taken subsequently to it. Lead arsenate was used in the 
spray and might have gathered in this dried juice which forms rough 
masses on the limbs and trunk of the tree. In order to remove as 
far as I might be able, such arsenic as might be present as lead 
arsenate, dust and other impurities, I dissolved the dried sap in as 
lit Lie warm water, not boiling, as possible and used onlv the aqueous 
solution in making the test for arsenic which was very abundant 
indeed. 
This sample of air-dried material gave 24.93 cent of lime, 
CaO; it contained a little magnesia and alkalies. I have made no 
attempt to determine the acid combined with the lime, but lime being 
practically the only base, it seems probable that the mass is essen- 
