Trees of New York State 371 



KEY TO THE SPECIES page 



1. Leaves densely white-tomentose when young, at length becoming green; 



pedicels of fruit 2/5-1 inch long A. canadensis 241 



1. Leaves essentially glabrous from the first; pedicels of fruit 1 1/5-2 inches long 



A. laeyis 241 



THE THORN-APPLES. Genus CRATAEGUS L. 



Low, wide-spreading trees or shrubs with usually dark or gray 

 scaly bark, rigid terete more or less zigzag branches often armed 

 with stiff sharp thorns, alternate simple leaves, showy flowers, and 

 pomaceous fruit. The genus attains its best development in east- 

 ern North America where many puzzling and intergrading forms 

 have been described. In New York State alone over two hundred 

 species are said to occur although the validity of some of these 

 is open to question. Undoubtedly several hundred species will be 

 found to be authentic, the bulk of which are found in eastern 

 United States, with scattered forms in the Rocky Mountains, on 

 the Pacific Coast, in Japan and Eurasia. 



Leaves alternate, deciduous, simple, serrate and sometimes variously lobed, 

 petioled ; stipules caducous or f oliaeeous on \-igorous shoots. Flowers perfect, 

 regular, showy, borne in simple or compound corymbs terminating short leafy 

 branchlets, the lowermost pedicels of a cluster often from the axils of the 

 uppermost leaves ; calyx-tube obconic, aduate to the ovary, the 5 lobes acute^ 

 leflexed and generally persistent; petals 5, white or pinkish, spreading, 

 inserted on the throat of the calyx, early deciduous; stamens variable in the 

 same species, normally 5 and alternate with the petals, but varying in multi- 

 ples of 5 up to 25 ; filaments subulate, incurved, often persistent on the fruit ; 

 anthers pale yellow to Avliite or from pink to dark rose and purple; pistil 

 consisting of a 1-5 celled inferior ovary crownied with a like number of styles 

 and stigmas; ovules 1-2 in each cell. Fruit a small, short-globose, oblong or 

 ])yriform pome, varying in color chiefly from red to yellow, containing 1-5 

 bony nutlets, each with a single upright seed. 



THE PLUMS AND CHERRIES. Genus PRUNUS (Tourn.) L. 

 Trees or shrubs with bitter astringent properties, slender branch- 

 lets, scaly buds, alternate simple leaves, showy flowers and drupa- 

 ceous usually edible fruits. Many contain prussic acid and exude 

 a gum from the barlv when wounded. The species of Prunus num- 

 ber about one hundred and twenty forms which are widely dis- 

 tributed throughout the temperate and tropical regions of the 

 northern hemisphere. Some thirty species occur in the United 

 States, eighteen of which are arborescent. In addition a number 

 of species from the Old Woi-ld have become naturalized. 



Leaves alternate, deciduous or persistent, simple, serrate or entire, petioled, 

 the petioles often glandular; stipules small, caducous. Winter huds scaly, the 



