124 IOWA ACADEMY OF SCIENCES. 



type is hard to break up; that those having behind them cen- 

 turies of unbroken strains of pure blood are hard to modify. 

 So, too, in the vegetable world, and in the case of crosses 

 between the unvarying native crab and the varying Pyrus 

 malus, the chances are altogether in favor of the crab's stamp- 

 ing its characteristics upon the offspring. P. lowensis is an 

 extremely variable species and so far as known it is only with 

 it that natural cross-fertilization has taken place in America. 

 The laws of correlation, of atavism, of prepotency, all the 

 uncertainties of heredity have yet to be explained in relation 

 to the vegetable kingdom, and until that is done, artificial 

 hybridization will be but a haphazard piece of work. More 

 attention must be given to the individual. 



PYRUS FUSCA RAFIN. 



Pyrus fusca Rqfin. Med. Fl. 11: 254: 1828-1830. 



Pyrus rivulm^is Dougl. in Hook. Fl. Bor. Am. 1: 213t. 68. 

 America South. 1833. 



Pyrus diversifolia Bongerd. Mem. Acad. Petersb. Ser. VI. 11: 

 133, 1833. 



Pyrus subcordata. Ledeb. Fl. Ross. 11: 95. 1844-46. 



Sometimes occurring as a shrub, usually a trea thirty to forty 

 feet in height, bark one-fourth of an inch thick, having the 

 surface broken into large, thin, loose, light brown scales; 

 leaves ovate to ovate-lanceolate, acute or acuminate at the 

 apex, pointed or rounded at the base, finely and sharply ser- 

 rate, often obscurely and occasionally distinctly three-lobed; 

 mature leaves thick, firm, dark green, glabrous, or slightly 

 pubescent above, pubescent below, one inch to four inches long, 

 one-half inch to one and three-fourth inches wide, borne on 

 rigid slightly grooved petioles one-half inch to one and one- 

 half inches long. The young leaves are covered both above 

 and below with long white tomentum. The flowers which 

 are borne in many flowered cymes are one-half inch in diam- 

 eter, calyx, densely tomentose on both inner and outer surfaces, 

 dropping before the fruit matures, in which respect it resembles 

 P. bascata. Petals orbicular, undulately margined, remotely 

 inserted; ovary three-celled, p3dic3l, slender, terete, one and 

 one-half inches to two inches long; the fruit " oblate-oblong" 

 one-half inch to three-fourths inch in length, greenish-yellow 

 or reddish when ripe; flesh dry, acid to the taste. Description 

 made from specimens received from A. H. Aiken, Doe Bay, 

 Washington. 



