THE ASH OF PLANTS. 195 



is not mentioned. Its absence, in many cases, is due, 

 without doubt, to the fact that chlorine is readily dissi- 

 pated from the ash of substances rich in phosphates or 

 silica, on prolonged exposure to a high temperature. In 

 some of the later analyses, in which the vegetable sub- 

 stance, instead of being at once burned to ashes, at a 

 high red heat, is first charred at a heat of low redness, 

 and then leached with water, which dissolves the chlo- 

 rides, and separates them from the unburned carbon and 

 other matters, chlorine is invariably mentioned. In the 

 tables of analyses, the averages of chlorine are undeni- 

 ably too low. This is especially true of the grains. 



The average of chlorine in the 26 analyses of wheat by 

 Way and Ogston, p. 150, is but 0.08%, it not being found 

 at all in the ash of 21 samples. In Zoeller's later anal- 

 yses chlorine is found in every instance, and averages 

 0.7%. In Lawes and Gilbert's numerous analyses of 

 wheat-grain ash chlorine ranges from to 1.14%, the 

 average being 0.1%. In wheat-straw ash they found 

 from 1.08 to 2.06%. The ash was in all cases prepared 

 by burning at a low red heat. 



Like sodium, chlorine is particularly abundant in the 

 stems and leaves of those kinds of vegetation which grow 

 in soils or other media containing much common salt. It 

 accompanies sodium in strand and marine plants, and, in 

 general, the content of chlorine of any plant may be large- 

 ly increased or diminished by supplying it to or withhold- 

 ing it from the roots. 



As to the indispensableness of chlorine, we have some- 

 what conflicting data. Salm-Horstmar believed that a 

 trace of it is needful to the wheat plant, though many of 

 his experiments in reference to this element were unsatis- 

 factory to himself. Nobbe and Siegert, who have made 

 an elaborate investigation on the nutritive relations of 

 chlorine to buckwheat, were led to conclude that while 

 the stems and foliage of this plant are able to attain a 



