POTATO DEVELOPMENT WORK IN WISCONSIN. 53 



VINE AND TUBER CHARACTERISTICS OF 



STANDARD MARKET VARIETIES 



OF POTATOES. 



PROF. WM. STUART, 

 Of the United States Department of Agriculture. 



I was somewhat surprised when I looked over a copy of the 

 program of this meeting, which I received a few days before leav- 

 ing Washington, to see that I was expected to lead a discussion 

 on the vine and tuber characteristics of standard market varie- 

 ties. The subject looks innocent enough, but like many innocent 

 looking things there are troubled waters below the surface. For 

 the past few years I have had the privilege of being able to study 

 a considerable collection of the standard varieties of potatoes, 

 and have endeavored to classify them into groups according to 

 well defined varietal characters of foliage or of tuber. The ma- 

 jority of our varieties fall very naturally into one or other of 

 these groups, but there are still quite a few which we have not 

 succeeded in classifying. 



We have found, for example, that it is a very easy matter to 

 distinguish between varieties belonging to the Green Mountain 

 and Rural New Yorker groups of potatoes. There are three dis- 

 tinct varietal characteristics in these groups on which no one can 

 err. Neglecting for a moment the shape and color of the tubers, 

 let us consider the color of the sprouts, preferably of those which 

 have g-crminated in the dark. You will find that the sprouts of 

 rJl vaiieties of the Rural New Yorker group are short and en- 

 larged at the base, of a dirty white color with tips and leaf scales 

 of a violet blue shade ; the Green Mountain group will all have 

 white sprouts which are not appreciably enlarged at the base and 

 which do not have any color in any portion of it. The stems of 

 the growing plants have a x^urplish hue in the Rural New Yorker 

 and light green in the case of the Green Mountain. The flowers 

 of Green Mountain are white, while those of Rural New Yorker 

 vary from a dark violet blue toward the center of an entire ab- 

 sence of color in the five points of the corolla. The intensity of 



