Medullary Spots in Wood. 251 



He found, for example, that some mountain ash and willow stems 

 have many pith flecks while other individuals of the same species 

 in the vicinity, often from the same root stock, did not show them. 

 Furthermore, he looked in vain for pith flecks in a large number 

 of birch and alder stems in a certain locality, though ordinarily 

 the wood of the Betulaccae contains them in abundance. Again, 

 in stems with pith flecks certain growth rings may be free of them 

 while others are thickly dotted. 



The present writer has observed pith flecks in the following 

 woods : Salix laevigata Bebb., S. Uuviatilis Nutt., Betula populi- 

 folia Marsh., B. papyrifera Marsh., B. nigra L., Ostrya virginiana 

 (Mill.) Koch., Pyrus rivularis Dougl., P. sambucifolia C. & S., 

 Amelanchier canadensis (L.) Medic, Crataegus crus-galli L., 

 C. punctata Jacq., Primus americana Marsh., P. pennsylvanicum 

 h. F., P. ilicifolia (Nutt.) Walp., P. Mollis Walp., Acer pennsyl- 

 vanicum L., A. saccharum Marsh., A. saccharinum L., A. rubrum 

 L., Ceanothus velutinus arhoreus Sarg., and Adelia acuminata 

 Michx. 



It is interesting to note that while pith flecks have been reported 

 in the woods of some fifty species and fifteen genera, no large 

 pored or ring porous woods are in the list. The oaks, ashes, 

 hickories, elms and similar woods are absent. The writer can 

 assign no adequate reason why this should be true, though the 

 character of the bark may possibly account for it. 



In view of all of the foregoing, the writer has come to the same 

 conclusion as Gayer,^^ viz : that as pith flecks "have a pathological 

 origin, and may be absent they should not be used in the identifi- 

 cation of woods." 



References Cited. 



1. Hartig, R. Die Unterscheidungsmerkmale der wichtigeren in Deutsch- 



land wachsenden Holzer. Munchen. 1879. 



2. Kienitz, M. Schliissel zum Bestimmen der wichtigsten in Deutsch- 



land cultivierten Holzer. Munchen. 1879. 



3. Nordlinger, H. Anatomische Merkmale der wichtigsten deuschen 



Wald- und Gartenholzarten. Stuttgart. 1881. 



4. Stone, H. The Timbers of Commerce and their Identification. Lon- 



don. 1904. 



5. Boulger, G. S. Wood. (Rev. ed.) London. 1908. 



6. Hartig, Th. Forstliche Culturpflanzen. 1840. Vollstandige Natur- 



geschichte der forstlichen Culturpflanzen Deutschlands. Berlin. 

 1851. 



7. Rossmassler, E. A. Versuch einer anatomischen Characteristik des 



Holzkorpers der wichtigeren Baume and Straucher. Dresden and 

 Leipzig. 1847. 



8. Nordlinger, H. Querschnitte von 100 Holzarten. Vol. II, p. 10. 



