PITH FLECKS OR MEDULLARY SPOTS IN WOOD. 

 By Samuel J. Record. 



Pith flecks or medullary spots are small, brown, half-moon 

 shaped patches appearing so commonly on the cross sections of 

 many of our woods, especially those of the four families Sali- 

 caceae, Betulaceae, Rosaceae and Aceraceae. All close observers 

 of wood are familiar with their appearance and several writers, 

 notably R. Hartig% Kienitz-, Nordlinger^, Stone*, and Boulger^, 

 have made use of them as one of the specific characters in wood 

 identification. The purpose of this article is to summarize in- 

 vestigations of the origin and nature of pith flecks, with special 

 reference to the taxonomic value of such occurrences. 



It appears that attention was first called to these spots by Th. 

 Hartig^ in 1840, terming them "cellular channels" (Zellgange). 

 He noted and described their occurrence in birch, red alder and 

 hazel. He made no attempt, however, to explain their cause. 



Rossmassler^ proposed the name "medullary recurrences" 

 (Markwiederholungen), believing the flecks to be of the same 

 formation as the rays. 



Nordlinger'^, in preparing his wood sections, remarked the oc- 

 currence of the spots in several species of wood and gave them 

 the name "pith flecks" (Markflecke), which has been generally 

 accepted. 



Cordes" and MohF" confirmed the statements of Th. Hartig 

 and Rossmassler regarding the species of woods in which the 

 flecks occurred. Ratzeburg" made some investigations of the 

 flecks which he termed "brown chains" (Braunketten) on account 

 of their color and horizontal distribution. He considered it pos- 

 sible but scarcely probable that they were due to the mining of 

 the cambium by the larvae of an insect which he provisionally 

 called Tipula suspecta. 



Kraus^^ made a more detailed study of the pith flecks with the 

 intention of using them diagnostically as a means of identifying 

 different kinds of woods but came to the conclusion that at least 

 in the case of the conifers they were inconstant and could not 

 safely be used in diagnosis. 



