AGRICITLTURAL BOTAXY, CHE.MISTRV AND PHYSIOLOGY OF PLANTS 957 



and they are compelled to push out their roots in order to get at it. In 

 this case again the peculiar property- of the variety (long-root system) has 

 been fixed by heredity and asserted itself in the trial cultivations. 



In addition to the length of roots, there were also studied : the total 

 weight of the plant, the weight of the overground and underground parte 

 separately, the distribution of the root stock in the different strata of the 

 soil. As regards the weight, it is found that the length of the root system 

 is not proportional to its total weight (see Table I) and that, in the majo- 

 rity' of cases, the roots, when increasing in length, show a relative reduction 

 in weight. With respect to the distribution of the roots in the different 

 layers (25 cm each) it varies greatly (as stated above) according to the variety. 

 On comparing the different varieties, however, it was found that No. 305 

 I for instance has long roots which are more abundant in the tilled stratum 

 of the soil than those of another kind with long roots, a fact which must 

 unquestionabh' be of very great importance. 



The studies of the other plants, spring wheat, flax and peas, as regards 

 difference of root lengths in the different varieties, confirmed the results 

 obtained with oats, which will probably also hold good for other cultivated 

 plants. For instance, Triticitm vulgare var. ferntgineum No. Ill has roots 

 90 cm in lengh, while those of Triticum dicoccttm var. farrum attain 182 cm. 

 The studies of flax were repeated in 1915 in boxes (they were unsuccessful 

 owing to the hail) and in the field. They bore on: (i) the " metric differ- 

 ences " of the root system in the different pure lines of the plant ; (2) the 

 constancy of depth of roots within the limits of the pure line ; (3) the influ- 

 ence of different soils and water (water cultures) on the growth of the 

 root system ; (4) the influence of moisture on the development of the root ; 

 (5) the development of the root at different vegetative periods ; (6) the daily 

 growth of the roots ; (7) the influence of the depth of seed-planting on the 

 development of the roots ; (8) the root system of the principal weeds 

 in flax fields ; (9) the stereometric distribution of the roots in the soil. The 

 most important results are as follows : 



Flax grown for fibre generally has a weaker and shallower root sj'stem 

 than that grown for seed ; if the root of the second kind reaches a depth 

 of 70 cm, that of the first does not exceed 40-57 cm. Moreover, the roots 

 of the seed flax are more robust, coarser and closer, a fact explained by the 

 southern origin of this plant, which endeavours to adapt its roots to an in- 

 adequate water supply. As regards root development at different periods 

 of vegetation, 3 periods have been distinguished : (i) the initial period, when 

 the flax plantlet has only 10 to 12 leaves; in this period the roots reach down 

 to a depth of 21 cm., maintaining a vertical direction; the distribution of 

 the roots in the different layers of soil is almost uniform ; (2) in the 2nd 

 period, the beginning of anthesis, the roots reach 52 cm, and the uniformity 

 of their distribution in the different layers disappears, the bulk of the roots 

 lying within the limits of 20 cm, representing the depth of the first period ; 

 beyond the second decimetre a considerable reduction in the mass of roots 

 is observed, only the few main roots with httle subdivision being found ; 

 (3) in the 3rd period, the end of anthesis, the roots reach a depth of 65 cm 



