GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 65 



however mild it may be, as not the slightest trace of growth could be detected 

 in the measured trees after the wonderfully mild winter of 1882. 



3. The British oak probably suffered a greater decline in its growth of 

 wood from the severe winters than any other tree under observation. The 

 Hungary oak, on the other hand, was less affected than- any other tree ; and 

 the Turkish and American oaks less than our native oak. 



4. In the wave of increase and decrease in wood growth through these 

 years the yews followed the deciduous class, and not their congeners the ever- 

 green pines. 



5. The appreciable growth of wood in deciduous trees is mainly confined to 

 June, July, and August in ordinary seasons ; but a material increase does take 

 place in May, particularly when the spring is unusually mild. 



6. The growing season in evergreen trees includes May, and probably an 

 appreciable start is made even in April, when the spring is favourable. 



7. The proportionate monthly growth seems to vary more in evergreens 

 than in deciduous trees. 



8. The growth of wood is probably greatest in July in deciduous trees, and 

 in June* in evergreens ; but further observations are required to settle these 

 points. 



9. On an average of three years the evergreen trees as a class accomplished 

 60 per cent, of their annual increase of wood before the end of June, the deciduous 

 60 per cent, of theirs after that date. Deodars appear to be exceptional, as 

 they agreed with the latter instead of the former group. In yews the growth is 

 probably pretty equally divided between the two periods. 



10. Of all the species measured, the Hungary oak and African cedar proved 

 much the quickest growers. Then followed the Sequoia gigantea. 



11. Thorough ripening of wood in autumn seems to be of immense con- 

 sequence in enabling deciduous trees to stand extremely low temperature in 

 winter. Evergreens however do not seem to be so dependent on it. 



12. An excessive rainfall seems to be favourable to the increase of wood, 

 particularly in evergreen trees. A great excess of rain in August 1881 appar- 

 ently stimulated the growth of wood in these to a remarkable degree, although 

 the temperature of the month was decidedly low. 



In conclusion, I cannot help expressing a wish that others who have better 

 opportunities than I can command would take up a line of inquiry which Sir 

 Robert Christison has made easy by the practical rules he has laid down for 

 its prosecution. The necessary observations are not difficult to make, merely 

 requiring precision ; and they take up little time when the trees experimented 

 upon are near at hand. The work is interesting, and the results may prove to 



* See foot note, page 57. 

 VOL. XXXII. PART I. L 



