468 Journal of Agricultural Research vol. i, NO. 6 



before black locust. The dogwood and persimmon sank in about 18 

 hours, while the catalpa floated for 20 days, and one piece of black locust 

 with a large percentage of heartwood remained floating for 46 days. 



SUMMARY 



The 143 specimens of hardwoods examined included 45 genera (94 

 species), of which 24 contained tyloses. The 60 specimens of conifers 

 examined included 13 genera (45 species), of which i contained tyloses. 

 Of the 139 species examined, 56, belonging to 25 genera, contair^d 

 tyloses. 



Tyloses were found in the sapwood of all species in which they occurred 

 in the heartwood. 



Well-developed tyloses were found in the outermost rings near the 

 bark of 30 species of hardwoods. 



True tyloses occur in the wood tracheids of certain pines, principally 

 of the white-pine group. 



Epithelial cells sometimes effect a partial or. even complete tyloselike 

 closing of the resin canals in Pinus, Larix, Picea, and Pseudotsuga. 



A considerable proportion of the vertical canals, even in the heart- 

 wood of the pines, are fully or partly open. 



Tyloses act like a natural filler in the hardwoods. 



The woods in which tyloses are abundant as a rule are durable. 



Tyloses, because they are very impermeable to air, water, and creosote, 

 reduce the penetrance of the woods in which they are strongly developed. 

 The presence of tyloses in the vessels of a hardwood, however, does not 

 prevent the penetrance of creosote into the other wood elements. 



LITERATURE CITED 

 BAILEY, I. W. 



1913. Preservative treatment of wood. In Forestry Quart., v. n, no. i, p. 



5-20, 2 pi. 

 BARY, ANTON DE. 



1884. Comparative Anatomy of the Vegetative Organs of the Phanerogams 

 and Ferns. Translated by F. O. Bower and D. H. Scott ... p. 170. 

 Oxford. 



BOEHM, JOSEF. 



1867. Ueber Function und Genesis der Zellen in den Gefassen des Holzes. In 



Sitzungsber. K. Akad. Wiss. [Vienna], Math. Naturw. Cl., Abt. 2, 



Bd. 55, p. 851-866, 2 pi. 

 1877. Ueber den aufsteigenden Saftstrom und den Abschluss lebender Zellen 



gegen aussere Einwirkungen. In Bot. Ztg., Jahrg. 35, No. 7, p. 112-113. 

 1879. Ueber die Function der vegetabilischen Gefasse. In Bot. Ztg., Jahrg. 



37, No. 15, p. 225-239; No. 16, p. 241-258. 

 CHRYSLER, M. A. 



1908. Tyloses in tracheids of conifers. In New Phytol., v. 7, no. 8, p. 198-204, 



Pi- 5- 

 HABERLANDT, G. F. J. 



1884. Physiologische Pflanzenanatomie. p. 217. Leipzig. 



1887. Ueber die Beziehungen zwischen Function und Lage des Zellkernes bei 



den Pflanzen. p. 71-74. Jena. 



