Germination of Forest Trees 65 
The species retained for this work were Pinus ponderosa (S. 
D.), Robimia pseudacacia, Quercus rubra, and Pinus strobus. 
Stem and root measurements were taken upon the first three of 
these species and stem measurements only upon the last one. 
Each measurement represents the average of 10 representative 
plants, except in case of Quercus rubra where from 3 to 14 
plants were used depending upon the number available. The 
measurements of the stems of Pinus ponderosa and Robima 
pseudacacia were taken at two different ages, namely at the age 
of two and three months, but the plants used at the age of three 
months were not the same ones used at the end of two months. 
Hence in the data the three months’ old plants are not necessarily 
larger than the two months’ old plants, although they usually are. 
Root measurements of Pinus ponderosa and Robinia pseudacacia 
were taken at the end of three months. Both stem and root 
measurements for Quercus rubra were taken at the age of five 
months. 
The effect of light on stem and root development is shown in 
the following table: 
Tue Errect oF Light on Stem AND Root DEVELOPMENT 
Conifers 
Stem Measurements Root Measurements 
P. ponderosa P. strobus | P. ponderosa (3 Mos.) 
Degrees 
2 Mos., 3 Mos., 2 Mos., Tap, Laterals, 
Cm, Cm. Cm. Cm. Cm. 
Opentlight ge pete 2.76 2.59 4.31 5-93 enti 
Medium shade............ 2.90 Bos 5-50 5.80 62 
Dense shade.............-. 3.50 be 6.35 Ae 
Hardwoods 
Stem Measurements Root Measurements (Tap) 
R. pseudacacia QO. rubra | Rob. pseud.| QO. rubra 
Degrees 
2 Mos., 3 Mos., 5 Mos., 3 Mos., 5 Mos., 
Cm. Cm. Cm. Cm. Cn. 
O) emai gta. en staal erels ee 6.00 7.02 9.40 9.64 13.8 
Medium shade........... 5.80 5.05 7.30 7.16 10.2 
Dense shade............:. 5-00 G52 6 BOO GOON ss TOL 
