Page ten 



EVOLUTION 



June, 1931 



Improving On Nature 



By RALPH H. McKEE 

 Professor of Chemical Engineering, Columbia University 



■piGHTY YEARS ago Ncw York was the leading lumber pro- 

 ■*-' ducing state in the Union and Pennsylvania was a close 

 second. Today these states have almost forgotten that they 

 once supplied the lumter or pulpwood for their own mills. 

 They use about twenty-five times as much as they produce. 

 About three years ago a commission was created by the New 

 York State legislature to make a survey of the wood industry 

 of the state. The commission found that, not only many mills 

 using tinber directly, but other industries as well, have moved 

 to locations nearer a source of wood supply. In fifteen years 

 New York lost more than 1200 wood-using industrial plants. 



States such as New York and Pennsylvania have four to 

 five million acres each of abandoned lands, lands which con- 

 tribute nothing to the prosperity and welfare of the state and 

 which have become a liability instead of an asset. Many of 

 these abandoned farms and cutover areas can be purchased 

 for from three to eight dollars an acre. To what better pur- 

 pose can this area be devoted than to plant it with trees? 



Growing trees appears to be a problem requiring genera- 

 tions rather than years or decades to give results. However, 

 using modern methods, this need not be so. 



It is common knowledge that agricultural crops, such as 

 wheat, oats, rice, corn, and so forth, have been improved by 

 hybridization and selective breeding. Among tree crops hybri- 

 dization has yielded conspicuous results in certain fruit and 



Three sister hybrid poplar seedlings, all from the same catkin. 

 Impossible to predict how crosses will turn out. 



*EXCERPT FROM JOURNAL OF FRANKLIN INSTITUTE. 



nut trees and in a few ornamental varieties. It is but logical to 

 expect similar improvement in forest trees suitable for pulp- 

 wood and lumber if we applied the methods of hybridization. 



Hybridization is, as you know, the cross-breeding of indi- 

 viduals of different species. The loganberry is a cross between 

 the antwerp raspberry and an 

 ordinary blackberry. Hybrids, 

 in general, grow faster, are 

 freer from disease, than either 

 of the parents. This is known 

 to geneticists as "hybrid vigor." 

 Unfortunately, hybrids do not 

 breed true and are often sterile. 



In considering the improve- 

 ment of trees for forest pro- 

 ducts the poplars seemed most 

 promising. There were five hy- 

 brid poplars in existence so we 

 knew that crosses could be ob- 

 tained. 



Our first problem was to lo- 

 cate the different varieties of 

 poplars in this country. The 

 largest collection was found to 

 be at Highland Park in Roches- 

 ter, the second largest at New 

 York Botantical Garden. Other 

 locations which furnished par- 

 ticular trees were Arnold Ar- 

 boretum in Boston, and certain 

 Long Island nurseries. 



Before the flowers on the fe- 

 male trees opened, paper sacks 

 were tied over the clusters to 

 prevent normal pollination. 

 Later, when the flowers opened, 

 pollen was obtained from the 

 flowers of the selected male tree. 

 The pollen was taken at once 

 to the female tree, and, by 

 means of a wad of cotton, diis- 

 ted over the female flowers. 

 The sacks were immediately re- 

 placed to prevent normal pollin- 

 ation. After about two weeks 

 the paper sacks were replaced 

 by green cheesecloth sacks.. I 

 might say that the only reason 

 for staining the sacks green 

 was to make them less conspic- 

 uous so that small boys would not throw stones at them. 



Six weeks later when the seed had ripened, they were re- 

 moved, taken to the laboratory where the cotton was carefully 

 picked off and the seed planted in damp sand. Nature pro- 



Hybridization, high in th< 

 tree, where flowers are. 



