IV.] FOOD STORAGE BY BIENNIALS 69 



carbohydrates into fibre — this latter a rearrangement we 

 did not consider in the case of wheat straw. The 

 formation of fibre is particularly marked in the final 

 stages when the seed of the grasses gets ripe, and as 

 fibre is an inferior food material to starch, not only less 

 digestible in itself but wasting much more labour in the 

 process of digestion, there results a considerable loss of 

 food value in the material. All this points to the 

 desirability of cutting hay in a young state ; the loss 

 of weight in the crop will not be great, because for the 

 bulk of the grasses the later stages of growth are not 

 attended by much increase of dry matter, since assimila- 

 tion becomes balanced off by respiration, while there 

 will be mechanical losses through the shedding of the 

 seed of many plants ; at the same time the much smaller 

 proportion of fibre in the early cut hay permits of a far 

 greater utilisation of the constituents of the hay by the 

 stock receiving it as food. 



The process of storage and migration of the 

 accumulated materials is perhaps most clearly seen in 

 the case of the biennial root crops like turnips and 

 mangolds (or fodder beet); the so-called bulb — an 

 enlarged stem in the case of swede turnips, a root in the 

 mangolds — is nothing more than a storage organ, and 

 the whole work of the first year's growth consists in 

 filling this with the carbohydrate assimilated by the 

 leaves and with the proteins which are also there 

 elaborated. In the mangold the material stored is cane 

 sugar, which constitutes about 60 per cent, of the dry 

 matter of the bulb ; the dry matter itself varies from 

 about 10-5 per cent, in the white-fleshed Globe variety 

 to over 1 3 per cent, in the yellow-fleshed and Long Red 

 varieties. In the sugar-beet, a form of mangold which 

 for more than forty years has been systematically bred 

 and selected for its sugar content, the percentage of 



