The Thorn Trees 443 



VI. THE THORN TREES* 



GENUS CRAT^GUS LINN^US 



PECIES of this genus occur in the north temperate zone, and southward 

 along the highlands of Mexico and South America, but eastern North 

 America is the center of its distribution, and here it ranges from 

 Newfoundland westward throughout the St. Lawrence basin and 

 southward all over the eastern United States, a few species occurring in the Rocky 

 Mountain States and on the Pacific slope. They are most abundant, both as to 

 varieties and individuals, in the limestone formations of the St. Lawrence- Great 

 Lakes region and the Missouri-Arkansas region, few occurring near the Atlantic 

 coast. 



Previous to 1899 about 65 species were known, about 25 of which were North 

 American, but since then over 600 species of these trees and shrubs have been 

 described. Many of these proposed new species have been based on such unstable 

 characters as the number of the stamens and the color of their anthers, and con- 

 siderable careful investigation will be necessary before the validity of many of 

 them is accurately determined. It seems likely that some of these forms are 

 natural hybrids between species. The trees here described seem to be distinct 

 species, and others which have been proposed may prove to be so when further 

 studied. 



They are usually spiny, much-branched shrubs or small trees, with dark brown, 

 scaly bark, the winter buds globose or subglobose, bright chestnut-brown. The 

 leaves are deciduous, alternate, simple, toothed, lobed or sometimes deeply cut; 

 the leaves of the young vigorous shoots are generally much larger, and often more 

 deeply lobed than those of the older branches; the stipules are linear, glandular- 

 toothed, deciduous, but on young shoots often large and persistent. Flowers 

 white, rarely some shade of red, borne in simple or compound cor}^mbs, generally 

 with linear, bright-colored, glandular, deciduous bracts; calyx-tube cup-shaped 

 or bell-shaped, adhering to the carpels, its 5 lobes pointed or long-pointed, gen- 

 erally glandular- toothed, rarely leafy, persistent on the fruit or deciduous; petals 

 5, rounded, inserted in the mouth of the calyx; stamens 5 to 25, often variable in 

 the same species; filaments thread-like, incurved; anthers oblong to suborbicular, 

 white, yellow, pink, or purple ; ovary inferior or its summit free, composed of from 

 I to 5 carpels; styles i to 5, free, commonly surrounded at the base by a tuft of 

 hairs; stigmas terminal, persistent; fruit subglobose, ovoid, oblong or pear-shaped; 

 red, green, yellow, purple, blue or black; flesh thin or thick, hard and dry in some 

 groups, soft, succulent or mealy and edible in others, containing i to 5 one-seeded 

 nutlets (in C. Oxyacantha 2-seeded); seeds erect, flattened. 



When the trees become better known they will be largely used in ornamental 

 planting, for screens, borders, and hedges, on account of their beautiful flowers, 

 which, by a proper selection of varieties, can be had from about May 15 to June 15, 



* Contributed by Mr. W. W. Eggleston. 



