20 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



I have also tried the Sycamore with a spiral curve cut out 

 of the bark, aud it gave as the result a spiral thickening 

 following the upper side of the cutting. The same thing is 

 seen in this ash walking stick, which I have shown in the 

 Society before, and in which the twining of a Honeysuckle 

 caused the interruption of the downward flow of sap sufficiently 

 to induce a spiral thickening of the stem above the spiral coil 

 of the binding Honeysuckle. The grains of the wood can be 

 seen to run in a natural perpendicular direction along the 

 central portion of the stick, but they take the spiral course in 

 the wood formed since the binding was effected. In this case, 

 instead of arresting the downward flow of assimilated sap, the 

 interruption only changed its direction. Following this change, 

 the cambium and hence the new conducting tissxie and the new 

 wood also change in such a way that the lengths of their cells 

 and vessels take the direction of the spiral instead of a course 

 parallel to the axis. The result is the formation of what looks, 

 in the distance, like one branch twined round another, but 

 which on closer inspection reveals its true origin. When this 

 stick was cut the Honeysuckle was still adhering tightly, and 

 the mark of it is yet clearly seen. Both below aud above the 

 portion round which the plant twined the thickening is normal, 

 and it is interesting to see how it passes from the normal to 

 the spiral below, and again from the spiral back to the normal 

 above. 



A few summers ago I chanced to come upon another interest- 

 ing case of changed direction of descending sap, in a wood near 

 Dinan. A Spanish Chestnut tree had some years previously 

 got its trunk cut right across one side, through the bark and 

 into the wood, and the result was a bulging growth to the 

 right and left. In this way the arrested sap got a passage 

 made past the cut part. The back of the tree showed nothing 

 abnormal, and both above and below all M'as going on in the 

 ordinary course. I have referred to the Ash stick and the 

 Spanish Chestnut in similar terms elsewhere.* 



The other subject of my recent experiments is the Lime tree, 

 and with it I find an important difference in behaviour. I 



* The Self- Educator Series, Botany, pp. 109-111. Hodder & Stoughton, 

 London, 1900. 



