6 Wisconsin Academy of Sciences, Arts, and Letters. 



On pine and larch the greatest growth had occurred at the base 

 of the trunks. By August 19 radial growth had ceased on 

 above-ground parts of broad-leaved trees, only a small amount 

 had occurred on the lateral roots and none on the fibrous roots. 

 In conifers radial growth was not entirely completed on aerial 

 parts and the roots were in about the same condition as those of 

 broad-leaved trees. In oak and maple radial growth on the 

 fibrous roots began about the 1st of August, in pine about the 1st 

 of September, in larch about mid-September. Hastings 12 found 

 that radial growth started first back of opening terminal buds 

 in broad-leaved trees and proceeded basad. By the time the 

 five to six-year branches were producing new wood radial growth 

 had become general all over the trees. In case of pine radial 

 growth commenced on the two to three-year old portions of 

 branches and apparently before the buds opened. It was 

 thought that perhaps growth started on two-year branches 

 in pine because leaves are retained two years, for it was noted 

 that in the hemlock, where the leaves are retained six to seven 

 years, radial growth seemed to have started first on six-year-old 

 branches, while in the bald sypress radial growth started first 

 just back of the opening terminal buds as in broad-leaved trees. 

 On the other hand Knudson 13 reports that radial growth begins 

 on young trees of the American larch in the fourth to six-year- 

 old branches. He holds that the cambium first gives rise to 

 phloem cells in spring and that wood cells are developed later 

 though his counts show only a few cells. The branches showing 

 the first radial growth were found in the middle region of the 

 tree. Here growth began at the apexes while in the trunk 

 xylem formation is said to start near the middle. Darkened 

 bark, owing to its heat absorbing qualities, is thought to induce 

 early growth. 



According to Goff 14 spring growth begins in many plants on 

 their roots. From his examinations in late March he reports 

 that the roots of Bibes vulgare had elongated as much as 7.5 cm. 

 (3 inches) before aerial growth had begun. Of the following 



" Hastings, G. T. When increase in thickness begins in our trees. 

 Plant "World. 3:113-16. 1900. Sc. 12:585-86. 1900. 



"Knudson, L. Observations on the inception, season and duration 

 of cambium development in the American larch. Bui. Torr. Bot. Club. 

 40:271-93. 1913. 



14 Goff, E. S. The resumption of root growth in spring. Wise. Agrl. 

 Expt. Sta. Ann. Rpt. 15:220-28. 1898. 



