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 Eibes vulgare had elongated as much as 7.5 cm. 
(3 inches) before aerial growth had begun. Of the following 
13 Hastings, G. T. When increase in thickness begins in our trees. 
Plant World. 3:113-16. 1900. Sc. 12:585-86. 1900. 
13 Knudson, L. Observations on the inception, season and duration 
of cambium develonment 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. 
