THE TWIST OF WOOD-FIBER IN THE TAMRAC PINE 

 Cornelius B. Bradley 



During my college days in Ohio I once heard a back-woodsman hold- 

 ing forth on the "twist" of the grain of the "Northfield Oak" of 

 Summit County. Its fibers, he affirmed, "always went round and 

 round the trunk with the sun," and he was sure that the sun's daily 

 movement across the sky caused the twist and determined its direc- 

 tion. I doubted the assertion that the twist in this species was in- 

 variably a left-hand twist, but I was perfectly sure that the sun's 

 movement did not determine its direction. If it did, then all exoge- 

 nous trees in our north temperate zone should have the same twist — 

 which notoriously they do not. The questions thus started made a 

 deep impression upon me, especially when I found out later that our 

 masters in botany had no answers to them — and so far as I can 

 learn they still have none. 



A summer vacation in the eighties, spent in the neighborhood of 

 a lumber-camp, showed me that my doubt as to the constancy of di- 

 rection of the twist in any given species of tree was well founded. 

 Both right-hand and left-hand twist occurred in every sort of tim- 

 ber cut there. In any given species, one direction was generally 

 more common than the other, but it did not then occur to me to as- 

 certain the ratios more definitely. 



Three years ago, however, as I came down the Tioga road from 

 the Meadows, there were stretches of forest where hundreds of tam- 

 rac pines (Pinus contorta var. murrayana) had been killed by the 

 borers, and were standing by the roadside stripped of their bark as 

 if awaiting physical examination. I at once recognized my oppor- 

 tunity and, pencil in hand, tallied the twist of some two hundred 

 and fifty of them. Eighty per cent showed the right-hand twist. A 

 few days later, in the remote and isolated Jack Main canon, I made 

 a similar tally which show T ed about seventy per cent of the left-hand 

 twist. These observations seem to indicate that the direction of twist 

 is a heritable quality, fairly well maintained along definite lines of 

 descent, though somewhat interfered with by variation or by ming- 

 ling with the opposite strain. 



In the interval between these observations I had spent a day in 

 camp at Porcupine Flat. There I looked up the leaf -arrangement of 

 the tamrac pine, and worked out the direction of its fundamental 

 leaf -spiral in a considerable number of trees about camp. I found 

 here again the same variation between right and left-hand spirals 

 that I had noted in observation of the twist of wood-fiber, and with 

 a like preponderance of the one over the other. 



This suggested, of course, a real connection of some sort between 

 the two phenomena. If at the time I had recognized the full signifi- 

 cance of the suggestion, I should at once have put the matter to the 



