FOE TEANSPLANTING ETEEGEEENS. 455 



temperature of August is more than 6° higher than that of 

 September, and of September than of October. Now as the 

 loss of water by trees is to a great degree dependent upon the 

 dryness of the air, it is obvious that in that point of view 

 August is almost four times as dangerous as October. 



It must also be borne in mind that perspiration in plants is 

 caused by the direct action of light, and that loss by perspira- 

 tion is in proportion to the length of time during which the 

 surface of plants is exposed to sunlight; heat and dryness 

 only increasing the amount. Now, in August the days are not 

 only longer but brighter than in September, and in September 

 than in October ; and here, again, the state of the atmosphere 

 is against the first month and in favour of the latter. 



If from these data alone we had to decide theoretically which 

 of the autumn months is the best, the choice would fall on 

 September; and this coincides with experience. August has 

 the advantage in the temperature of the soil, but is too dry and 

 light. In September dryness and Hght have become more 

 moderate ; the temperature of the soil has not fallen more than 

 4°, and evergreens then planted have two clear months in 

 which to form new roots. October has the advantage in a 

 lower temperature and more diminished light ; but the soil is 

 6° colder than in September and it leaves the worst of two 

 months for new roots to develope in. For such reasons it 

 would seem that September is better than either August or 

 October, October than August or November, and August better 

 than November. 



Macnab rightly adverts to the importance of choosing a 

 Suitable day, as weU as season, for the operation ; and it must 

 be evident from what has now been stated, that this is very 

 necessary : " In winter, you may plant with perfect safety in a 

 duU calm day, whereas in spring or autumn a moist rainy day 

 is preferable to any other; but where a person has not the 

 choice of such weather, then the work should be performed in 

 the evening, when the sun gets low, especially in spring or 

 autumn planting." 



Next in importance to the selection of a fitting season, is the 

 preservation of the roots of transplanted trees ; the former is 



