228 . SHADE-TREES IN TOWNS AND CITIES 



which constitute the plantation of which they are to form 

 a part. For this purpose a nursery has to be maintained 

 where trees of different species and sizes are grown, ready 

 to take the place of trees that fail. 



The method outlined above is followed in Paris. The 

 trees that are to be trained for transplanting, to take the 

 place of large specimens, are set out in the municipal nursery 

 about twenty feet apart each way to allow room for develop- 

 ment. The branching is gradually raised and then fixed at 

 the proper height. Every three or four years the roots are 

 cut or circumscribed so that they do not spread out, but are 

 made to grow compactly, restricted within a certain volume. 

 This work of cutting the roots consists of digging a circular 

 ditch around the base of the tree and cutting the roots as 

 neatly as possible. The size of the ditch depends upon 

 the size of the tree. Thus in the case of a tree about four 

 inches in diameter, three feet from the base, the circular 

 ditch is about three feet in diameter and about two and one- 

 half feet deep. After the roots have been cut the soil is 

 replaced and closely packed. 



In the cases of trees that have been trained as described 

 above, the Board of Works of Paris prescribes the dimen- 

 sions of the ball of earth and roots with which trees of dif- 

 ferent sizes are to be transplanted about as follows: 



