The second group is distinguished by the firm, breaking flesh of the fruits--the Bigarreaus of several languages, the name originally having reference to the diverse colors of the fruits. This group is further divisible in accordance with color of fruit and juice into black Bigarreaus and light Bigarreaus. Chief of the black cherries falling into this division are Windsor, Schmidt and Mezel; of the light ones, which are much more numerous, Yellow Spanish and Napoleon are representative sorts. Linnaeus called these hard-fleshed cherries _Prunus avium duracina_; De Candolle called them _Cerasus duracina_; K. Koch, _Prunus avium decumana_; and Roemer, _Cerasus bigarella_. Besides these two orchard forms of _Prunus avium_ several other horticultural forms, quite as distinct or even more so, are grown as ornamentals, some of which are listed as distinct species or as botanical varieties of _Prunus avium_. To add to the confusion, a number of Latinized garden names are more or less commonly applied to these ornamental Sweet Cherries. Schneider,[9] in revising the genus Prunus, names four botanical forms of _Prunus avium_ and two natural hybrids with other species. [9] Schneider, C. K. _Handb. Laubh._ =1=:1906; =2=:1912. PRUNUS AVIUM × PRUNUS CERASUS The Duke cherries, long placed by most pomologists and botanists in a botanical variety of _Prunus avium_, are unquestionably hybrids between the Sweet Cherry and the Sour Cherry. A study of the characters of the varieties of the Duke cherries shows all gradations between _Prunus cerasus_ and _Prunus avium_, though, in the main, they resemble the latter more than the former, differing from the Sweet Cherries most noticeably in having an acid flesh. Sterility is a common attribute of hybridism. In this respect the Dukes behave like most hybrids. In several Duke cherries all of the seeds collected at this Station are sterile; in others, most of them are sterile and in none are the seeds as fertile as in varieties known to be pure bred as to species. So, too, shrunken pollen grains indicate hybridity. A study of the pollen of the Duke cherries shows many grains, the greater proportion, to be abnormal, a condition not found in the pollen of varieties true to species. May Duke, Reine Hortense and Late Duke are the leading hybrid varieties. [Illustration: PRUNUS AVIUM × PRUNUS CERASUS (REINE HORTENSE)] There are dark colored Duke cherries with reddish juice and light colored sorts with uncolored juice, just as in the two parent species. May Duke is a typical variety with colored juice while Reine Hortense is probably the best-known cherry among these hybrids with uncolored juice. About 65 of the cherries listed in _The Cherries of New York_ are "Dukes," or hybrids between the Sweet and the Sour Cherry.