Alnus.
Alnus. Alder.—Of this genus of small trees or bushes, A. glutinosa (L.) Medic., or European Alder, Black Alder; A. rugosa (Du Roi) K. Koch (A. serrulata Willd.., or American Alder; A. incana (L.) Willd., or Tag Alder, are tonic and. astringent, and have been used in intermittent fever, the bark being the part employed. A. glutinosa has been used for dyeing and also for tanning. According to Eitner, the bark contains from 16 to 20 per cent. of tannic acid. The tannic acid, however, appears to differ from that of galls and oak bark, as, according to Stenhouse, it does not yield glucose when acted on by sulphuric acid. (P. J., Dec., 1861.) F. Dreykorn and E. Reichardt, however, state that it is resolved by sulphuric acid into alnine red and sugar. (A. J. P., xlii, 403.)
