Jan. 1898] BOTANICAL SOCIETY OF EDINBURGH 103 



rains of 1872, '73, and '74 do not appear to have affected 

 the rise, except that without so much raiu the rise might 

 have been greater. 



The fall from 1876 to 1879 occurred during a period of 

 heavy rainfall, low sunshine, and low temperature. The 

 dry, warm, sunny summer of 1880 caused a rise; then 

 came a fall imtil 1885, during which time sunshine and 

 temperature were low, and rainfall high. 



The rise from 1885 to 1890 occurred during a drier 

 and warmer period. 



The fall in 1891 and 1892 agreed with that of most 

 of the other trees, as also did the rise of 1893. Scots 

 pine agrees with larch in preferring warm, sunny seasons, 

 but it also grows well in wet seasons, provided they are 

 also warm ; and cold, wet seasons hinder its growth 

 considerably. Spruce prefers moist seasons ; it does not 

 stand prolonged drought, and even a warm, sunny period 

 is against its growth, if at the same time the rainfall is 

 low. 



I have to thank Mr. Percival C. Waite for helping me 

 with the calculations; Mr. William T. Finlayson, my 

 assistant, for part of the drawings and colouring of the 

 diagrams; and Mr. William M. Miller, my laboratory 

 assistant, for valuable assistance in drawing and colouring 

 the diagrams and curves. 



APPENDIX. 



" It is beyond doubt that the mean temperature is of much less 

 importance to forest trees than the extremes of temperature which 

 occur in a particular locality, more especially during the growing 

 period." — Schlich's "Manual of Forestry," 1st ed. vol. i. p. 36. 

 According to Gayer— " Der Waldbau," by Dr. K. Gayer, 1882— the 

 relative heat requirement is greatest in Scots pine, less in spruce, and 

 least in larch. 



•'Trees suffer, as a rule, little from winter frosts within the region 

 of their natural distribution, but frost which occurs during the growing 

 season may do considerable damage, especially during spring." — 

 Schlicb, vol. i. p. 115. 



"The late frosts in spring and the early frosts in autumn often 

 occasion very considerable damage, especially to young growth. 

 Danger from frost is greater on plains than in hilly tracts ; greater on 

 S. and S.E. exposures than on N. and W. ; greater in localities pro- 

 tectel from the wind than in those where currents of air have free play ; 

 greater in a dry state of the atmosphere than in a moist." — Nisbet's 

 " British Forest Trees," p. 27. 



