682 TREES OF NORTH AMERICA 



1. Koeberlinia spinosa, Zucc. 



Leaves not more than ' long. Flowers appearing in May and June, about \' in 

 diameter. Fruit yY~V in diameter. 



A bushy tree, rarely 20-2o high, with a short stout trunk sometimes G-8 long 



and a foot in diameter; more often a low branching shrub forming impenetrable 

 thickets often of considerable extent. "Wood very hard, heavy, close-grained, dark 

 brown somewhat streaked with orange, becoming almost black on exposure, with thin 

 yellow or nearly white sap wood of 12-15 layers of annual growth. 



Distribution. Dry gravelly mesas and foothills; valley of the lower'Rio Grande, 

 Texas, westward to southern Arizona, and southward through northern Mexico. 



XLII. CARICACE.ffi. 



Trees or shrubs, with bitter milky juice, alternate long-petiolate persistent 

 simple or digitatoly compound leaves, without stipules. Flowers unisexual or 

 perfect, the perianth of the male and female flowers dissimilar ; stamens in 

 two series, inserted on the corolla ; filaments free ; anthers introrse. Fruit 

 baccate. 



The Pawpaw family with two genera is tropical American and Mexican, a 

 single representative of one of the genera reaching the shores of southern 

 Florida. 



1. CARICA, L. 



Short-lived trees, with erect simple or rarely branched stems composed of a thin 

 shell of soft fibrous wood surrounding a large central cavity divided by thin soft 

 cross partitions at the nodes, covered with thin green or gray bark marked by the 

 ring-like scars of fallen leaf-stalks, and stout soft fleshy roots. Leaves simple, pal- 

 mately lobed or digitate, crowded toward the top of "the stem and branches, large, 

 flaccid, subpeltately palmately nerved, and usually deeply and often compoundly 

 lobed. Flowers regular, monrecious or polygamo-dicecious, white, yellow, or greenish 

 white, in axillary cymose panicles, the staminate elongated, pedunculate, and many- 

 flowered, the pistillate abbreviated and few or usually 3-flowered, generally unisex- 

 ual and dioecious, occasionally polygamo-dioecious, each flower in the axil of a minute 



