Varieties of fi.ooTS. 



143 



the loss of leaf surface by the plants might have an influence on the 

 sugar content and dry matter content of the roots. Part of the rota- 

 tion plat kept almost free from leaf-spot. No efforts were made to 

 check the spread of the disease. 



The results showed a „ _ _ . ^ 



gain of 1.9 tons in yield, or ' ^^^i^^^a 4^HKa^. T 



21 per cent, on the rotation 

 plat. This, with the higher 

 dry matter and sugar con- 

 tent, ensured a yield of half 

 a ton more dry matter per 

 acre or 24 per cent, increase. 

 It is noteworthy that this 

 increase was entirely in 

 sugar, the increase in this 

 ingredient being 45 per cent. 

 The increase in dry matter 

 and sugar was well main- 

 tained from the earliest har- 

 vesting until the last. The 

 number of plants per acre 

 was fairly uniform through- 

 out the plat, averaging 

 34,000. The yield of tops 

 per acre weighed immedi- 

 ately after harvesting was 

 a little heavier than the 

 yield of roots, and the 

 amount of foliage on the 



Fig. 53. — Carter Model kohlrabi. A variety 

 heavy in dry matter. ' Adapted to a wider 

 season of sowing than rutabagas and man- 

 gels. On a 6-inch screen. 



' no rotation " portion was somewhat 



greater than on the " rotation " portion. 



History and development of the mangel: 



Von Thaer states that the mangel wurzel in his time was a kind of 

 red beet and that it was a mongrel between the red beet (garden type) and 

 the white beet, a cross which might readily occur. 



In the i8th century it was popularly known in Germany as " the root 

 of scarcity," and it was under this name that it was introduced into Eng- 

 land by Dr. John Coakley Lettson about 1785. About this time, 1786, 

 Mr. Thomas Boothby Parkins transmitted an account of the root from 

 Metz to the London Society, with seeds. McMurtrie states that the 

 variety sent was that named Disette by Vilmorin, which was the long 



