Variations in Anatomical Structure 



665 



Table VII. — Carya ovata, same specimen as table IV. Average length of 



vessel-segments in millimeters 



Diameter of Vessels at Different Ages of a Tree 



Table VIII. — Carya ovata, same 

 specimen as table IV. Large ves- 

 sels. 



Diameter Vessels, 

 A nnual Millimeters 



Rings Max. Min. Ave. 



Section 2 feet from ground 

 2-5 0.24 0.20 0.21 

 29-37 0.41 0.29 0.33 

 57-65 0.41 0.31 0.37 



Section 19 feet from ground 



19-27 0.38 0.28 0.33 

 47-55 0.42 0.36 0.38 



Section 46 feet from ground 



0-8 0.24 0.14 0.18 

 28-36 0.38 0.27 0.33 



T.A.BLE IX. — Carya ovata, same speci- 

 men as table III. Large vessels. 

 Section 2 feet from ground. 



Diameter 



Discussion and Conclusions 



A. Size of tracheary elements in different parts of a tree. 



In 1872 Sanio^ published the restilts of a detailed study of the 

 variations in size of the tracheids in Scotch pine. From his ob- 

 servations upon the conditions in this plant, he deduced a number 

 of conclusions in regard to the variation in size of the tracheary 

 elements in conifers. The first of these says: In the stem and 

 branches the tracheids everyw^here increase from within outwards, 

 throughout a number of annual rings, until they have attained a 

 definite size, which then remains constant for the following anntial 

 rings. 



' Sanio, Karl, Ueber die Grosse der Holzzellen bei der gemeinen Kiefer 

 {Pinus silvestris L.). Jahrb. Wiss. Bot., Vol. VIII, pp. 401^20, 1872. 



