138 
Journal of Agricultural Research 
Vol. XXIV, Na a 
The results of the two determinations are shown in Table XIV. 
Table XIV.— Sa/> density of trees in iq 20 transpiration tests (whole plants) 
Species. 
Yellow pine 
Pot 
No. 
Average 
Bouglas fir..... 
I . Average. 
Ijodgepole pine. 
Average.... 
i^ngelmann spruce 
i. 
I ... . 
I Average.... 
l|iniber pine. 
Bristlecone pine... 
Sjcotch pine. 
Siberian larch. 
22 
I 
i8 
IS 
Source. 
Harney... 
-do. . ; . 
Bitterroot. 
Tusayan.. 
9 
19 
12 
II 
16 
21 
8 
4 
2 
13 
6 
20 
Hayden.. 
Leadville 
Pike. 
Colorado. 
Washakie 
Gunnison, 
San Isabel. 
Montezuma, 
San Isabel., 
Unknown... 
Unknown. 
-do_ 
.... do_ 
-do_ 
Russia.... 
-do_ 
_do_ 
-do_ 
Sap density at— 
Beginning 
of season. 
End of 
season. 
Per cent. 
13- 15 
• “ 13- IS 
• ^ 13- 50 
12. 71 
Per cent. 
16. 18 
15. 59 
13. 01 
9 * 30 
13* 13 
13.52 
15. 24 
• ^15-50 
15.63 
13 - 25 
13.71 
IS-17 
14. 20 
14.72 
• ^ 14 - 65 
14. 49 
10. 60 
8. 80 
10. 38 
14.5s 
9. 93 
, 13. 70 
^ 13 - 65 
9. 91 
13. 50 
Lost. 
12. 84 
12. 93 
12. 32 
12. 69 
12. 70 
16. 05 
® 16. 05 
15.75 
® 15. 75 
10.43 
® 10. 43 
8- S 4 
“ 8.54 
13. 02 
® 15. 36 
16. 29 
15. 68 
10. 80 
12. 65 
^ 13. 75 
^ IS* 05 
Seasonal 
change. 
+0.39 
-.97 
— 4. 62 
+. 01 
-I. 86 
+. 23 
+1. 29 
+5. 86 
jo One test only for this class of material. 
extracted. Sap density estimated from green-dry ratio 
3}® specimen of high sap density is the one that made practically no growth. 
“P 
IH considering Table XIV it should be borne in mind that at the time 
potting the trees for transpiration study some of the species had made 
ry appreciable grow^ while others had probably felt the stimulus of 
little. It is perfectly apparent from other data secured that 
me imtia^on of growth in the spring means a flooding of the plant with 
^ter. sap densities of spruce and Siberian larch 
are expressive of their response to relatively low temperatures, while that 
of yellow pine is more indicative of a low condition throughout the 
Winter^ 
In view of the fact that the stage of the seasonal advance had affected 
the reveral species differently, it is questionable whether the spring data, 
or the changes throughout the season, have any great value in our 
present comparisons. 
