Canadian Forestry Journal, September, 1919 



351 



WHEN TREES GROW! — A NOVEL STUDY 



By Prof. J. S. lllick. Chief, Department of Silviculture, 

 Pennsylvania Department of Forestry. 



What Four Years' Daily Measurements of 200 



Trees Disclosed — Common Conceptions 



Proved Erroneous. 



Editor's Note: In Pennsylvania the northern and southern forests have a common meeting 

 place. No doubt a study in Ontario or Quebec similar to that of Prof. Illicit would alter the 

 data in .some degree, but at the same time the conclusions likely would not differ materially. 



PROF. ILLICK'S CONCLUSIONS: 



Trees grow almost twice as much at night as during the day. 



White pine and Norway spruce cease growing (in Pennsylvania at least) by July 1st. 



Such {(nowledge is of high utility in choosing the season for transplanting youns trees. 



Nothing about the numerous processes of trees vegetative rest alternates with a period of 



is more readily comprehended than that they vegetative activity. I propose to present for 



grow, for the results of growth are so obvious, your consideration some interesting and essential 



and in some cases striking, particularly in tern- facts pertaining to the growth behavior of our 



perate regions where annually a period of common forest trees: Growth, however, is such 



I'lioto by 



.^. lllick. 



The new growth of N'or\\;i\' Spruce is llcxibK- and 

 droopiii;^ l'i>r :i lniri' | .i-idd immediately after tln' 

 maxiniuni li(i,i;lu uinwili dl' the season has bci'U 

 laid 1)11. 



Photo by .1. S. lllick. 



'rcriniiKil twigs of Norway Spruce arc crt>ci and 

 <tilT at tlie cn;l of the RrowiiiK sc ison. 



