OF SAP liN PLANTS. 23 



dinal section showed that the liber had absorbed strongly ; and 

 light blue, not sharply defined streaks, corresponding to the 

 course of the tracheae, were seen in all parts of the wood ; the 

 thin pith remained unaffected. On the whole the reaction was 

 weak, because the great mass of the fluid had already ascended 

 into the higher parts of the plant. 



2. A young sycamore stem {Acer plat anoides), 3 inches in dia- 

 meter, was watered with the ferrocyanide in the ground ; but 

 this could not be detected in a small quantity of fluid which ex- 

 uded from boring. It appeared to have been wholly decomposed 

 by the (ferruginous) soil, since this had acquired a blue colour. 



3. The soil at the base of a young sycamore of 1|^ inch dia- 

 meter was watered, on the 26th of February, with a weak solu- 

 tion of the ferrocyanide. On the 28th holes were bored into the 

 stem, but the drops which exuded did not react with salt of iron ; 

 neither did the ^ of a drachm of fluid that was found on the 1st 

 of March. No more exuded after this. The soil around was 

 coloured blue, and when the stem was cut off on the 10th, no 

 ferrocyanide could ^be detected in it. 



The small efflux of sap in these two young trees, 2 and 3, was 

 remarkable. 



4. The earth round the trunk of a sycamore, 4 inches in dia- 

 meter and 35 feet high, was watered with solution of the ferro- 

 cyanide on the 2nd of March ; a hole. A, was then bored in the 

 stem 1 foot above the ground ; the vessel attached to this was 

 rapidly filled with fluid. Tolerable quantities of fluid flowed out, 

 and in part down, continuously during the following days, but 

 on the 7th of March no ferrocyanide could be discovered in it. 

 On this day the soil round the tree was watered a second time 

 with one ounce of a more concentrated solution ; the orifice con- 

 tinued to pour out freely. On the 9th the soil was watered a third 

 time, and a new hole was made (on the north side) at the same 

 height as the old one (on the south side). On the 10th of 

 March the fluid which had trickled from A gave a dark blue 

 precipitate with sulphate of iron, which was not the case with 

 B. On the 11th no reaction on either side. On the 12th no 

 more had exuded ; on the 14th therefore the tree was cut ofl" at 

 the base, and three pieces of it separated and examined, from 

 the base, the middle, and the summit. The two lowest pieces 



