172 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



food of the American ludians, especially those of California and certain parts 

 of Mexico, and tliey are still employed to some extent. Acorns contain starch, 

 fixed oil, citric acid, sugar, and astringent and bitter principles. Sometimes 

 they are sweet enough to be eaten raw without preparation, but usually it la 

 necessary to rid them of the bitter principle. This is done by shelling and 

 skinning the seeds, then pounding them into meal. The meal is washed re- 

 peatedly in water and then boiled as a mush or baked as cake or bread. 

 White oaks (subgenus Leucobalanm) have the sweetest and most palatable 

 acorns and have been the most generally used. All the live oaks (such as 

 Qucrcus virginiana, Q. pungetis, and Q. obUmyifolia) are said to have edible 

 acorns, but the black oaks (subgenus Erythrobalanus) were not extensively 

 employed. The Indians of the southeastern United States obtained from the 

 acorns of Q. virginiana a sweet oil much used in cooking. In more recent times 

 acorns have often been roasted and employed as a substitute for coffee, or 

 as an adulterant of it. 



Oaks are of little importance in medicine. In Mexico the staminate catkins 

 are reputed anodine and antispasmodic, being used as remedies for vertigo and 

 epilepsy. The bark and acorns are sometimes used as astringents. 



One of the most interesting products of these trees is the lac, widely known 

 in Mexico, which is produced by certain scale in.sects, or Coceidae. This, pre- 

 sumably, is produced on various species of oaks, and also upon trees and shrubs 

 of other families. The following account, by Urbina,' of its production upon 

 Quercus reticulata, may be quoted here : 



"It seems worth while to mention here tlie manna which forms on Quercus 

 axniminata H. B., an oak which grows at INIedina, on the boundary between 

 the States of Michoacan and Mexico, which was studied by Sr. D. Melchor 

 Oeampo, who gave the tree the name of Quercus meUifera, its vernacular name 

 being encina de mid. According to Dr. Oliva (Lecc. Farm. 2: 84), in May it 

 produces an abundance of a globular rough substance, which turns black and 

 resembles manna. Sr. Dr. D. ilanuel M. Yillada brought back from an ex- 

 cursion which he made to iMedina a branch of this tree, black as if the bark 

 were covered with rubber, due to a fungus which had formed in such quantity 

 that it gave ri.se to a thick layer, in whose midst appeared very fine threads, 

 long and transparent, like caramel, and which, in my opinion, are produced by a 

 Coccus or aphis which feeds on this sugary substance. The excess is emitted 

 in threads whose peculiar form is due to the abdominal tubes of the aphis. 

 The explanation of this seems to me to be the following: In the month of 

 May there is an abundant secretion of glucose produced by the bark of the 

 oak, which is taken advantage of not only by the aphis which make these 

 caramel-like threads, but also by the fungus which attacks the bark. 



" Under the circumstances, I believe it desirable that a study be made of 

 this product, which, in the opinion of Sr. Oliva, may be a manna, a presump- 

 tion apparently justified by the existence of two organisms; the fungus and 

 the Coccus, which develop simultaneously, using the same food — the glucose. 

 And as this principle is the dominant one in manna, I believe with Sr. Oliva 

 that this oak under favorable conditions produces this substance, which should 

 be analyzed carefully, after visiting the place where the oak grows, and study- 

 ing the manner of its formation, in order to comfirm or correct this view." 



The vernacular names applied to the species of oaks can be given in only a 

 few instances. Many names are found in literature, but the species have 

 been so confused that no confidence can be placed in the determinations. The 

 usual Spani-sh names are "encina" (live oak) and " roble " (deciduous oak), 



' Naturaleza 7: 105-106. 1900. 



