I02 THE GRAPES OF NEW YORK. 



the various species clearly and distinctly. Many of the earlier descrip- 

 tions, while they are correct so far as they go, do not mention enough 

 characters to enable one to distinguish between similar species. It has 

 been found that dependence upon the shape of the leaf, size of berry, size 

 of plant, date of ripening, and similar characters, is very uncertain and 

 unsatisfactory and that, while these characters are always mentioned in 

 descriptions as indicating the intrinsic value of a species, they are of little 

 value from a systematic standpoint. There are, however, several char- 

 acters of Vitis which have great taxonomic importance. 



One of the fundamental characters which determine a species is con- 

 tinuous or intermittent tendrils, first noticed by Professor A. Braun' of 

 Berlin. Vitis labnisca, the common Fox grape, is peculiar in that there 

 are tendrils, or an inflorescence, opposite nearly every leaf; this arrange- 

 ment is known as continuous tendrils. All other species have two leaves 

 with a tendril opposite each and a third leaf without a tendril : such species 

 are said to have intermittent tendrils. Continuity of tendrils is a variable 

 character and to ascertain which of the two forms is present it is necessary 

 to have vigorous, healthy, typical canes. The lowest leaves of canes usu- 

 ally have no opposite tendrils. This character is shown in the color-plates 

 of the several species. 



A closely related character is that of the number of inflorescences 

 borne b}' a species. All species excepting Vitis labrusca average two 

 inflorescences to the cane but the last named species, at least in some of 

 its subdivisions, may bear from three to six inflorescences, each of course 

 in the place of a tendril opposite a leaf. 



Professor Millardet of Bordeaux first called attention to the value of 

 that part of the cane known as the diaphragm as a means of distinguishing 

 species. The cane of the grape vine contains a large pith, and in most 

 species this pith is interrupted by woody tissue at the joints; this woody 

 tissue is the diaphragm. The presence or absence of the diaphragm and its 

 thickness are of taxonomic value. In Rotundifolia, the southern Fox grape, 

 the diaphragm is absent; in Riparia, the Riverbank grape, it is very thin; 

 in Rupestris it is slightly thicker; while Cordifolia, Aestivalis, and Labrusca 

 have thick diaphragms. This character is studied best in the year-old canes 



' Mo. Etit. Rpt.. 1874:71. 



