Periodical Literature. 451 



this field points out the hypothetical condition in which the theories 

 are left. 



Ueber das Konstructionsprincip des sekunddren Holzkorpers. Natur- 

 wissenschaftliche Zeitschrift fur Forst-u. Landwirtschaft, 1908, as re- 

 viewed by Dengler in Zeitschrift f. Forst-u. Jagdwesen. April, 1909. Pp. 

 272-276. 



Another contribution to the knowledge of 

 Identification wood structure comes from the botanical 



of Woods. laboratories at Harvard in the form of an 



anatomical study of the wood of the pine 

 family. The wood of the genus Picea heretofore has been char- 

 acterized by the entire absence of wood parenchyma. By making 

 slightly oblique tangential sections, Bailey found wood paren- 

 chyma upon the outer surface of the summer wood in seventeen 

 species, American and foreign. The occurrence of such cells, 

 however, is extremely sporadic. They were distinguished only 

 with difficulty in the species of northeastern America. 



It is stated in Penhallow's North American Gymnosperms that 

 spruce wood lacks spiral thickenings of the tracheids. The writer 

 of the paper found them well developed in the summer wood up 

 to the tenth year in seventeen species. In wood formed later than 

 this, they were very sporadic in occurrence. 



The investigator uses the above points, together with others, 

 to show the futility of distinguishing woods by any one charac- 

 ter, especially is this true of the genera Picea, Larix and Pseu- 

 dotsuga. In fact, to distinguish them one must refer to all of 

 the anatomical characters as well as to the gross characters. 



The Structure of the Wood of the Pineae. Botanical Gazette. July, 

 1909. Pp. 47-55- 



A thorough and accurate knowledge of the 

 Microscopic microscopic structure of wood is as es- 



Structure sential to investigators and users of pre- 



of servative and seasoning processes, and to 



Wood. the use and identification of woods as a 



knowledge of anatomy is to the modern 

 physician. Take for example the injection of preservatives and 

 the drying of wood. An accurate understanding of the struc- 

 ture of water conducting elements and the method by which fluids 

 pass through wood is essential to the development of successful 



