101 



THE WALNUTS— JUGLANS, L. 



Bfhis genus comprises about 15 species which are found chiefly in 

 the north temperate zone. Five species are native to North Amer- 

 ica, two of which are native to Pennsylvania. In addition to the 

 native species a European species known as the English Walnut 

 {Juglans regia L.) is widely distributed in the United States as an 

 ornamental tree. It is this European species which yields the val- 

 uable Circassian Walnut wood used so extensively in the manufac- 

 ture of furniture and it also produces the English walnuts so com- 

 mon on our markets. 



Our native species produce materials which are of considerable 

 commercial importance. The wood is highly prized. The nuts are 

 delicious and valuable as a food. The bark and husks are used as 

 dyes and tans. The wood of our species is dilfuse-porous and brown 

 to black in color. The leaves are alternate and compound. The 

 pith is chambered. The fruit ripens in one season and consists of a 

 sculptured or rugose nut covered by a pulpy husk which does not 

 split open into regular segments. The kernel of the nut is 2-4 

 lobed, large and oily. The nuts are scattered mainly by rodents, 

 which bury them for food, and by floods which carry them along 

 their courses. 



SUMMER KEY TO THE SPECIES. 



Page. 



1. Leaflets 11-17, often viscid-hairy, tlie terminal leaflet usually present; pitli dark 



brown; bark gray; fruit sticky-hairy; nut elongated-ovate J. cinerea 102 



1. Leaflets 13-23, not viscid-hairy, the terminal leaflet often absent; pith light brovra; 



bark dark brown; fruit not sticky-hairy; nut globose, J. nigra. 103 



WINTER KEY TO THE SPECIES. 



1. Bark gray; pith dark brown; nut elongated-ovate; upper surface of leaf -scar not 

 notched; hairy transverse fringe above leaf -scar present; terminal buds evidently 

 flattened, not less than i of an inch long, J. cinerea 102 



1. Bark dark brown; pith light brown; nut globose; upper surface of leaf-scar notched; 

 hairy fringe above leaf-scar absent; terminal buds slightly flattened, J of an 

 inch or less in length, j. nigra lOS 



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