1915] BROWN—PINUS STROBUS 241 
36. DeVries, H. Uber den Einfluss des Drucks auf die Ausbildung des 
Herbsthol. Flora 55:241-246. 1872; 5§8:97-102. 1875. 
. WIELER, A., Beitr. zur Kenntnis ek Jargon und des Dicken- 
wachstums. Pringsh. Jahrbiich. 18: 70-132. 
ber die nee 2 in der ei der Pflanzen. Forstw. 
Centralbt: 16: 333. 
, Uber die jahrliche Periodicitaét im des oars der Baume. 
Thar. Forsil: Jahrb. 48:39-139. 1808. 
w 
~I 
w 
? 
EXPLANATION OF PLATES XIII AND XIV 
Fic. 1.—Cutting III taken from tree I, December 22, 1912; cambium and 
phloem in the resting condition; 
Fic. 2.—Cutting I taken from ten I, February 20, 1913; phloem (A-B) 
in winter 2 contin: X16 
Fic. 3.—Cutting IV, same; contraction from low temperature more 
restricted; > 160. 
Fic. 4.—Cutting I taken from tree I, April 26, 1913; eee taking place 
very rapidly (c, approximate position of the cambium); 
Fic. 5.—Cutting II taken from tree I, May 12, 1913; vapid xylem forma- 
tion has occurred (c, approximate position of the cambium); X 50. 
IG. 6.—Cutting IV taken from tree I, September 19, 1913; transitional 
forms Gs tracheids, slow growth; 
7-—Cutting IIT taken from Gee I, September 26, 1912; autumnal 
eee of the phloem; X 200. 
Fic. 8.—Diarch white pine root before secondary thickening; two exarch 
bundles in process of formation; Xgo. 
Fic. 9.—Tetrarch white pine root after secondary thickening; X 25. 
Fic. 1o.—Same enlarged, showing 4 original xylem rays; 
Fic. 11.—Long roots and short roots of white pine, May to, 1913. 
Fic. 12.—New growth of long roots, May 14, 1913. 
