IXFLUENCE OF THE LOSS OF LEAVES ON TURNIPS. 27 



the grain of cereals ; with this difference, however, that 

 the skin does not become empty, as is the case with the 

 latter on germination, but is always re-filled and keeps 

 increasing in size. The perennial plant always receives 

 more than it expends ; whereas the monocarpous plant 

 spends its whole store in forming fruit. 



The fact that the roots of the tmniip, in autimin, grow 

 at the cost of the constituents of the leaves, readily 

 explains the influence which the removal of leaves will 

 exercise upon the crop at different stages of growth. 

 The removal of a few leaves in Ausrust makes no sreat 

 difference to the root, while the removal of leaves at the 

 end of September causes the greatest damage to the root- 

 crop. Metzler, who made very accurate comparative ex- 

 periments upon this point, found that an early cutting of 

 the leaves reduced the turnip crop by 7 per cent, only, 

 while a late, or a second cutting, reduced it by as much as 

 36 per cent. 



If, in the first year, instead of the turnips bemg removed 

 from the field at harvest, the tops were merely cut off and 

 the roots were left and ploughed in, the field would, on 

 the whole, sustain a loss of soil constituents ; still the roots 

 in the soil would retain the greater portion of them. A 

 very different relation would arise, if at the end of the 

 second year of vegetation the turnip tops were cut off, and 

 the stem were removed together with the seed. For, at 

 the end of the first year, the root would still retain the 

 far larger portion of the azotised and also of the incom- 

 bustible constituents, which would thus be left in the soil ; 

 but in the second year these materials would be carried 

 into the overground part of the plant, and there be used 

 for the production of the stem and the seed ; hence, the 

 removal of the latter would of course make the soil poorer, 

 even thou«jh the roots were now left in it. Before the 



