2l6 REPORT OF THE FOREST, FISH AND GAME COMMISSION. 



its roots against the glass sides. From time to time the boxes are pulled out of the 

 ground and the root growths observed and recorded. 



Observations upon white pine, Scotch pine, silver fir, beech, oak, birch and 

 maple have been carried on for three years on plants aged from one to six years. 

 During the winter, from November till March or April, the roots of the needle 

 trees, as observed in the boxes, make no growth. Those of deciduous trees, on 

 the contrary, do not go through this period with complete rest, but grow wher- 

 ever the temperature becomes mild, even in midwinter. In February and the 

 beginning of March, however, the roots show very little growth. 



It is noticed that in the spring the roots begin to develop before the buds, in 

 some cases several weeks. The larch and alder are an exception to this rule. 

 The buds of these species have been observed to unfold even a month before the 

 roots started. 



Since the soil has a temperature below that of the lower air it follows that the 

 roots begin their growth at temperatures lower than that necessary for the develop- 

 ment of the aerial parts. The minimum temperature necessary for the growth of 

 needle trees, as recorded by a thermometer placed in the boxes, is from five to six 

 degrees Centigrade ; for the maple and beech, from two to three degrees. 



The roots have also a summer rest, in August and September,- a time when 

 the water content of the soil in the nursery is at its minimum. This interruption 

 may last from three to eight weeks, according as the summer is wet or dry. Then 

 follows in October a period of more active growth and of longer duration in the 

 deciduous trees than in the conifers. 



The most rapid development takes place at the beginning of summer. The 

 oak has its maximum at the end of June or the beginning of July. The root 

 growth is then about 3.54 inches a day, that of the fir and Scotch pine about 

 2.36 inches. From these observations a judgment is formed as to the most favorable 

 time to plant trees in the forest. For the success of a plantation it is essential that, 

 as soon as the trees are placed, the roots should enter upon a period of active 

 growth to replace the water taken from the tree by evaporation. On the other 

 hand, the plantation should be made when transpiration is at its minimum. These 

 conditions are usually best secured in the spring. In a country, however, where 

 the spring is usually dry and the fall mild and moist, the plantation should be 

 made in the autumn. 



For deciduous trees to grow well when planted in autumn they must form 

 root hairs before the arrival of the great cold, and must lose very little water by 

 evaporation during the winter. Hence, in countries where the winter is very cold 

 and dry these, as well as the conifers, should be planted in the spring. 



