JUGLANDACE^ 125 



larly fissured, broken into thin plates, about ^' thick. Wood light, soft, spongy, 

 pale brown or yellow. 



Distribution. High desert plateaus from southwestern Texas to southern Arizona, 

 southward into northern Mexico; most abundant and of its largest size on the eastern 

 slope of the continental divide in southern New Mexico and along the northern rim 

 of the Tucson Desert in Arizona. 



Division II. Dicotyledons. 



Stems formed of bark, wood, or pith, and increasing by the addi- 

 tion of an annual layer of wood inside the bark. Parts of the flower 

 mostly in 4's and 5's ; embryo with a pair of opposite cotyledons. 

 Leaves netted-veined. 



Subdivision 1. Apetalae. Flowers without a corolla and some- 

 times without a calyx. 



Section 1. Flowers in unisexual aments (^female flowers of 

 Juglans and Querciis soUtaty or in spikes^ ; ovary inferior 

 (^siqjerior in Leitneviacece) when calyx is present. 



V. JUGLANDACEiE. 



Aromatic trees, with watery juice, terete branchlets, scaly buds, the lateral 

 buds usually superposed, 2-4 together, and alternate unequally pinnate decid- 

 uous leaves with elongated grooved petioles, and without stipules, the leaflets 

 increasing in size from the lowest upward, penniveined, sessile, short-stalked or 

 the terminal usually long-stalked. Flowers monoecious, opening after the un- 

 folding of the leaves, the staminate in lateral aments and comj^osed of a 36- 

 lobed calyx in the axil of and adnate to an ovate acute bract, and numerous 

 stamens inserted on the inner and lower face of the calyx in 2 or several rows, 

 with short distinct filaments and oblong anthers opening longitudinally ; the 

 pistillate in a spike terminal on a branch of the year and composed of a 1-3- 

 celled ovary subtended by an involucre free toward the apex and formed 

 by the union of an anterior bract and 2 lateral bractlets, a 1 or 4-lobed calyx 

 inserted on the ovary, a short style with 2 plumose stigmas stigmatic on the 

 inner face, and a solitary erect orthotropous ovule. Fruit a nut inclosed in an 

 indehiscent or 4-valved husk, its walls and partitions more or less penetrated 

 by internal longitudinal cavities filled with dry powder. Seed solitary, 2-lobed 

 from the apex nearly to the middle, light brown, its coat thin, of 2 layers, with- 

 out albumen ; cotyledons fleshy and oily, sinuose or corrugated, 2-lobed ; radicle 

 short, superior, filling the apex of the nut. Of the six genera of the Walnut 

 family two occur in North America. 



CONSPECTUS OF THE NORTH AMERICAN GENERA. 



Aments of staminate flowers simple, sessile, or short-stalked ; husk of the fruit indehiscent ; 



nut sculptured ; pith In plates. 1. Juglans. 



Aments of staminate flowers branched, long-stalked ; husk of the fruit 4-valved ; nut not 



sculptured ; pith solid. 2. Hicoria. 



