l8 AGRICULTURAL RESEARCH AND THE FARMER : 



followed in both cases by spring-sown bariey. The yield of the 

 crops is determined, and throughout the experiment examinations 

 of the soil are made in order to trace the course of the decom- 

 position of the green crop and the production of nitrates, and also 

 to examine the effects of the crop on the physical condition of the 

 soil, particularly as regards its moisture content. 



The Growing Crop. Farm Weeds. 



We pass on to refer to some aspects of the investigations in 

 progress in the Botanical Department of the Institute. In the 

 first place a careful study is made year by year of the effect of 

 various mixtures of manures on grass land, attention being paid 

 not only to the yield of hay secured but to the botanical composi- 

 tion of the herbage. The field trials are the classical Parle Grass 

 Plots, which have been studied in this way since 1855. The 

 results are weU known and appreciated, and it is unnecessary 

 to refer to them in detail. It may be mentioned, however, that 

 of recent years special attention has been paid to the effect of 

 liming on the occurrence of individual species, the most striking 

 facts emerging being that on well manured soil the application 

 of lime results in a decided increase of the useful Foxtail grass 

 and a decrease of the less useful grasses, Yorkshire Fog and Sweet 

 Vernal. 



The field experiments are supplemented by pot trials and by 

 growing plants in water-culture under various conditions of 

 treatment. This applies particularly to the case of cereals, and 

 a noteworthy feature in connection with the root development of 

 these plants which has recently been studied in some detail may 

 be mentioned. By growing individual plants of barley and wheat 

 in pots under varying manurial treatments, and carefully ex- 

 amining the root systems, it was found that the addition of 

 manures resulted in a considerable increase of what are usually 

 known as the " white roots " of the plant, the effect of the manures 

 being somewhat different in the two cereals. These " white 

 roots " are developed at the time the plant tillers, that is, throws 

 out new shoots. They issue from the crown of the plant, remain 

 unbranched for a long period, tend to grow laterally instead of 

 downwards, and are clothed throughout their length with root 

 hairs. As it is the root hairs — which normally only survive near 

 the tips of the rootlets^ — which foiTn the absorbing organs of the 

 plant, the capacity of " white roots " to absorb food supply from 

 the soil is greatly increased. An examination of the structure 

 of " white roots " of barley showed that, compared with ordinary 

 roots, their internal anatomy was modified to suit the needs of 

 a rootlet that is absorbing extra large quantities of water contain- 



