THE ASH OF PLANTS. 217 



The " lodging " of cereal crops is demonstrated to re- 

 sult from too close a stand and too little light, which 

 occasion a slender and delicate growth, and is not per- 

 ceptibly influenced by presence or absence of silica. 

 Silica, however, if not necessary to the life of the cereals, 

 appears to have an important office in their perfect de- 

 velopment under ordinary circumstances. Kreuzhage 

 and Wolff have carefully studied the relations of silica to 

 the oat plant, using the method of water-culture. In a 

 series of nine trials in 1880, where, other things being 

 equal, much silica, little silica, and no silica were sup- 

 plied, the numbers of seeds produced were 1,423, 1,039, 

 and 715 respectively, the corresponding weights being 

 46, 34, and 23 grams. The total crops weighed 196, 

 172, and 168 grams respectively, so that while the yield 

 of seed was doubled in presence of abundant silica, the 

 total crop (dry) was increased in weight but one-sixth. 

 The supply of silica was accompanied with an absolutely 

 diminished root-formation as well as by a relatively in- 

 creased seed-production. Similar trials in 1881 and 1882 

 gave like results (Vs. St., XXX, p. 161). Wolff con- 

 cludes that silica ensures the timely and uniform ripen- 

 ing of the crop as well as favors the maximum develop- 

 ment of seed. 



The natural supply of silica appears to be always suf- 

 ficient. Application of this substance in fertilizers has 

 never proved remunerative. In those water-cultures 

 where large seed-production has been obtained in ab- 

 sence of silica, it is probable that lime-salts, phosphates, 

 or other ash-ingredients, which are commonly taken up 

 more abundantly than in field culture, have brought 

 about the same result that silica usually effects. This 

 action of the ash-ingredients is apparently due to a clog- 

 ging of the cell-tissues and consequent check of the pro- 

 cesses of growth and would seem to be caused either by 

 the otherwise unessential silica or by an excess of the 



