i<po8.] IMPROVEMENT OF THE POTATO. 383 



potato that Carrolus Clusius Atrebatis, in his Rariorum Plantarum Historia 

 published by Moretus in 1601, declared to have been sent to him by Philippe de 

 Sivry a Vienne at the beginning of the year 1888. These two tubers and the 

 seeds from this fruit have produced all the potatoes which at the end of the 

 sixteenth century were cultivated in Austria, Germany, Switzerland and France." 



Judging from this plate and from what Clusius says in his "Rar- 

 iarum plantarum historia" (17), the plant has changed little under 

 cultivation except probably to give fewer and larger tubers. The 

 larger tuber shown in the figure is one and three-fourths inches long 

 and would weigh about 35 grams. He states in his work that the 

 plant then yielded as many as fifty tubers of unequal size and from 

 one to two inches long. This would still be considered a good yield 

 for a two-year seedling and is commonly not exceeded here the 

 first or second year by unacclimated varieties imported from Europe. 



The other European introduction, that into Great Britain, 

 was first described by John Gerard in his "Herbal," published in 

 London in 1597. This has usually been given as the first descrip- 

 tion of the potato and the accompanying figure is a reproduction of 

 his wood-cut as given in the edition of 1636. Gerard, however, 

 knew of Clusius' description as is shown in the following quotation. 

 He says, speaking of the potato : 



"It groweth naturally in America, where it was first discovered as reporteth 

 Clusius, since which time I have received roots hereof from Virginia otherwise 

 called Norembega, which grow and prosper in my garden as in their own 

 native country." 



It is remarkable that these two introductions into Europe were 

 made with two different varieties of S. tuber osum. The one de- 

 scribed by Clusius which probably produced the earlier varieties of 

 northern Europe, had reddish tubers and light purple blossoms. The 

 later introduction into England described by Gerard possessed light 

 brown to yellowish tubers and violet to almost white flowers. 



The variations in the descendents of these two varieties have 

 been almost entirely restricted to the tubers. The ash-leaved varie- 

 ties of England constitute an exception, where the variation is in the 

 shape of the leaf. This fact is important from two points of view. 

 First, it indicates that there has been but little correlated variation 

 between underground and aerial parts, and hence we are unlikely to 

 find plant characters by which we can with reasonable certainty re- 

 ject unsuitable types. Second, zuith so little visible variation in the 

 plant, there is likely to be narrow variability in resistance to fungus 

 diseases, should such resistance be due to structural differences. 



