Germination of Forest Trees 69 
next greatest in the loam. In the case of Pimus ponderosa clearly 
the greatest length is either in the loam or in the gravel and the 
shortest length of stem is in the sand. Loam and gravel are, as 
we have seen, quite opposite when it comes to moisture retentive- 
ness, hence the good development of plants grown in gravel must 
be attributed to other properties of gravel, namely, the amount 
Tue Errect or Soil Texture upoN STEM AND Root DEVELOPMENT 
Conifers 
| Stem Measurements | Root Measurements 
Degrees F 12 BOLAND P. strobus | uf ponderosa (3 MOS) 
2Mos., 3 Mos., 2 Mos., Tap, Laterals, 
Cm. m. Cm. m. Cm. 
[Boater seme eb ha yh 2576 2.59 4.31 BLOB ee bake 
SPAT VG Laat Cre ee ren hee | IS} 2.06 ZE8 02a 0222 | 94 
(Grae ara t Bae) oy tele nc oo 2.05 2.70 4.10 Woo ALOR 
£ 
Hardwoods 
Stem Measurements Root Measurements (Tap) 
Degrees R. pseudacacia Q. rubra | Rob. pseud.| Q. rubra 
2 Mos., 3 Mos., 5 Mos., 3 Mos., 5 Mos., 
Cm. Cm. Cm. Cm. Cm, 
a fe 
| 
TB OATS epee eases oN ts wine 6.00 7.02 9.40 9.64 | 13.80 
MS EVI GL ps easy cores) conse ceantemaiens careers 4.75 4.75 5.90 10.85 | 15-70 
(Gravelam case acon 3.80 4.25 5.70 TORT eT OFOO 
of air in the soil. Pinus strobus shows the greatest height growth 
in the sand. Robinia shows the greatest length of stem in the 
loam and the least in the gravel. This is in peculiar contrast to 
Pinus ponderosa. For growth Robinia is evidently more par- 
ticular about soil moisture than about the amount of air in the 
soil. Quercus rubra shows the greatest height growth in the 
loam and the least in the gravel. 
The tap root of Pinus ponderosa is of greatest length in the 
gravel and least in the loam, and the total length of lateral roots 
is greatest in the gravel. This naturally follows from the fact 
that, as has been pointed out before, gravel allows water to 
"percolate rapidly and the top layers dry out very soon, hence the 
