250 Muhlenberg's observations on the 



name of Pachgammah (beaten-wood) given to it by 

 the Indians. 



QUERCUS.* 

 Of the oak I shall only here notice those species 



* Of all trees and shruba, oaks and willows prove the most difficult of 

 Botanical investigation ; the former because their leaves vary very much 

 according to the soil, the situation, and climate in which they grow; the 

 latter because the observer has not always an opportunity of comparing 

 both sexes, and because they are apt to produce hybrid offspring ; to 

 which may be added, that the form of their leaves is likewise subject to 

 change from the soil, and the different periods of their growth. As for 

 the oaks, "It is so much the more difficult to distinguish species from varie- 

 ties, as they have been but little observed in their native countries. Of 

 such of the above species as I have had an opportunity of examining, I 

 shall attempt giving the specific characters. W. 



Since the publication of thispaper, M. Mi chaux, a native of Charles- 

 town, in South Carobna, and well known as an indefatigable traveller 

 In the service of Flora, has published a work of great utility on the same 

 subject, under the title, Histoire des Cbenes de V Amerique on description et 

 figures de touies les especes et varietes de chenes de I' Amerique septentrionale. a 

 Paris, 1801. fol. Aware of the great confusion in which the North Ame- 

 rican species of this difficult genus were involved, this botanist has sown 

 and cultivated, during his residence In America, all the species he had an 

 opportunity of procuring. By this means he became, indeed, enabled to 

 mark the multiplied variations through which they pass, until they 

 arrive at their full growth, and to discover their mutual affinities; but 

 on the other hand he found it a matter of great difficulty to distinguish 

 and define many of them by true and constant specific characters. Find- 

 ing that neither the structure of the sexual parts, nor that of the acorns 

 and their cups proved sufficient for his purpose, he finally had recourse to 

 their leaves. The leading character taken from these, is their being with 

 or without terminating bristles. A subordinate character is derived from 

 the time that intervenes between the first appearance of the flowers, and 

 the fruit's arrival at maturity. Some ripen their fruit within six, others 

 not in less than eighteen months. Of the former tbc fruit is perma- 



