EVAPORATION AS A CLIMATIC FACTOR. 55 



portant factor in this whole subject of plant development and plant life. 

 The nursery trade generally will tell you the fall is the time to plant 

 anything deciduous. You go through the nurseries and they are going 

 all around — pulling the leaves ofif every tree. What is that for? It is 

 to make the purchaser think that tree has shed its leaves and has got its 

 season's growth, and secondly, they know if that tree is put up with 

 those leaves on, the evaporation is going to exhaust the tree immediately 

 and it will lose its life and it is going to die. The evergreen is a tree 

 that carries its leaves the year around. It is not like a tree that sheds 

 its leaves. There is a point to it, to which sufficient attention is not given, 

 and I think it is extremely important because, as Dr. Livingston and Dr. 

 MacDougal stated, there is a point beyond which, if the moisture of the 

 plant is exhausted below a certain point, you have reached the death- 

 point beyond which life cannot endure. By this investigation that has 

 been indicated in this paper, I think we are going to get a great deal 

 of light on these important matters. 



Dr. Hansen — It has been our experience in our nursery work in 

 the northwest (that means the northern part of the Mississippi valley) 

 that the fall planting of all trees means death to a tree. They are usually 

 dry enough to burn by spring. A tree has no chance whatever to es- 

 tablish communication with moisture in the soil, especially evergreens. 

 It is sometimes said that our dry winter winds will take the moisture 

 from a fence post. 



The President — There is no doubt about it. 



Dr. Hansen — Another point I have noticed in the spring is that the 

 fruit trees in the nursery have the young shoots shriveled very much, 

 and in the early spring it is unsafe to dig too much because the shoots 

 are so shriveled that they lack moisture. They have had more moisture 

 evaporated in the winder than there was in the twig, but by leaving them 

 for a few days in the spring after a rain, they plump up and the shoots 

 absorb enough moisture from the air, it is presumed, so that they have 

 assumed a plump appearance. I think this question of evaporation is 

 an important factor. 



.1/;-. Southwick — I have in my notes here, a lecture given in this 

 hall, in which it was stated that an elm tree evaporated lOO tons of 

 moisture a day, and that an acre of grain — it does not say what was 

 on it — evaporated one hundred tons of water in a day. Is that so? 



The President — That is a remarkable statement. That is the trouble. 

 A great many of us get hold of a truth and try to kill it in every way 

 we can by exaggeration. 



Mr. Siebrecht—l do not believe in late fall planting of evergreens. 

 If you can transplant them early enough so that they will get at least 

 three weeks or six weeks of warm weather with moisture with it, and 

 you get nearly all the roots — I think under such favorable conditions, 

 you can make our evergreens live. They will make small fibres, and if 

 you will only take them along, they are all ready to spring. That is to 



