Germination of Forest Trees 45 
According to that classification the most drought enduring are 
Pinus divaricata, Pinus resinosa, Robinia pseudacacia, and Acer 
rubrum. It is rather unusual to find Acer rubrum in this cate- 
gory but the seed has such a thin seed coat that water absorption 
is easier than in the case of a thick-coated seed. The intermediate 
species are Pinus strobus, Pinus palustris, Abies balsamea, and 
Catalpa speciosa (Neb.). Among what might be called the 
moisture loving species are found Pinus taeda, Catalpa speciosa 
( Ind.), Quercus rubra and Betula papyrifera. 
On page 44 are given the germination curves of Pinus divari- 
cata and Robinia pseudacacia. These sets of curves show that 
as soil moisture decreases the beginning of germination is delayed, 
the germination curve rises less rapidly and the final germination 
per cent. is decreased. 
RABE Wi 
Tue Errect oF Soil Moisture on GERMINATION 
Rocky Mountain Species 
Dry Soil Medium Wet Soil Wet Soil 
oO » ~ ra 
BA] 29 |B 5/89/28 jes | gA | eo jes 
TU SE pO GCTOSG yer ‘S.1D); 26 | 26 | 26.0] I2 | 36 | 48.0] 10 | 32 | 58.0 
TUN WSe PONG CLOS Gey erste Harney] 34 © GO) 22 | aS | wo) weAl |) aeat || Ao) 
IZ OUS OPUAOSU ooh aoc 84 N.M. | 22 | 18 | 39.5] 20 | 16 | 61.0] 14 | 40 | 56.0 
Pseudotsuga taxtfolia...... N.M. | 12 @ | SoH 22 |p AVI |) SA0)) 2a || QO | O8-O 
Pseudotsuga taxifolia...... Colo: || 2A || BA © I2 | 42 | 60.5] 12 | 42 | 91.0 
VPAIGTESACOWGOLOVA meee olen Colo. | — | — —/| 80 | 26 | 12.0} 24 | 50 | 38.0 
JEGOMS COMA ob 06006008 Colo. | — | — =| 2O. || OO |) BoGil Zl |) GO || Beso 
Pinus ponderosa.......... Mon. | — | — | — 18 | 58 6.0] 18 , 12 | 10.0 
Pseudotsuga taxtfolia...... Mon. |} — | — ——|| £8 | 26" | T2-0)) 24) |) 34 20.5 
Pseudotsuga taxifolia...... Idaho | 24 |) O25] ZO || B® || Os) US|) BO || Boss 
PINUS Ponderosa. «3... + ++ Idaho | 90 8 | 5.0] 14 | 72 | 2r.0| 36 | 52 | 42.0 
PAIDUES OVO GTS eee eine Idaho | — | — —| 66 | ro | 3.0] 36 | 36 | 4.0 
Abies lasiocarpa.......... Idaho | — | — 84 I T.0/ 30 | 30 | 6.0 
LVS TROUHEQUO oc 5abevoo Idaho | 48 Tl OLSe LS ese OOle24 | 50) 2285 
As in the preceding table, Table V shows that the beginning 
of germination is delayed in most cases and that the germination 
period is considerably shortened with the decrease of soil moisture 
content. Only I species, Pimus ponderosa (N. M.) showed a 
higher germination per cent. in the medium wet soil than in the 
wet soil, all other species show a higher per cent. in the wet soil. 
