5(56 JOURNAL or FORESTRY 



younger and therefore more vigorous than the larger trees. While 

 further investigation is needed to determine how generally applicable 

 are the results of this experiment, two conclusions may be drawn from 

 it: (1) that sample plots to study the effect of different degrees of 

 thinning should be composed of trees of as nearly as possible the same 

 size; (8) that as a rule thinnings may be profitably undertaken at an 

 earlier age than is now customary, S. T. D. 



Mer, E. Influence de la diniension des arbres stir I'efficacite des eclaircie^. 

 Rev. Eaux et l^orets. 57:141-146; 165-175. 1919. 



UTILIZATION, MARKET, AND TECHNOLOGY 



Generally the vertical elements of woods are 

 Ripple Marks interlaced in such a way that they do not lie in 

 In Wood definite horizontal layers or strata, but in a con- 



siderable number of the dicotyledons some or all 

 of the elements are found to be so arranged. This regular storied 

 arrangement gives the appearance of the "ripple marks" seen most 

 clearly on the tangential section as fine parallel lines more or less wavy 

 or ripplied and running in a direction cross-wise of the fibers or hori- 

 zontally in the tree. Professor Record presents in this article a sum- 

 mary of his own study of this peculiar feature of the structure of 

 woods, and also a review of the investigations of other scientists. 



A remarkable fact noted in the article is that there is no close correla- 

 tion between this peculiarity of wood structure and the various types of 

 floral organization which serve as the basis of the botanical classifica- 

 tion. There appears to be some relation, on the other hand, between 

 this storied arrangement and other features of the wood structure. 

 It is of interest to note that with few exceptions (Aesculus, Cercis, 

 Cytisus, Diospyros, and Tiha) the woods are of tropical or subtropical 

 origin. 



This storied arrangement may be only that of the vessel segments or 

 of one of the other elements alone as tracheids or parenchyma cells, 

 or even of some one characteristic, such as the pitting near the ends of 

 the fibers and in other cases it may be that all of the elements are so 

 arranged. Sometimes a secondary or intermediate striation is pro- 

 duced by the shorter parenchyma cells forming two to four layers to 

 each one layer of vessel segments. 



The lines are frequently more easily seen by unaided eye than 

 under the microscope, since the accumulative effect is lost at the high 



