THE ASH OF PLANTS. 167 
Experiments in Solutions.—Water-Culture.—Sachs, 
W. Knop, Stohmann, Nobbe, Siegert, and others have 
likewise studied this subject. Their method was like that 
of Prince Salm-Horstmar, except that the plants were 
made to germinate and grow independently of any soil; 
and, throughout the experiment, had their roots immersed 
in water, containing in solution or suspension the sub- 
stances whose action was to be observed. 
Water- Cultwre has recently contributed so much to our 
knowledge of the conditions of vegetable growth, that 
some account of the mode of conducting it may be proper- 
ty given in this place. Cause a 
number of seeds of the plant it is 
desired to experiment upon to ger- 
minate in moist cotton or coarse sand, 
and when the roots have become an 
inch or two in length, select the 
strongest seedlings, and support them, 
so that the roots shall be immersed in 
water, while the seeds themselves shall 
be just above the surface of the liquid. 
For this purpose, in case of a single 
maize plant, for example, provide a 
quart cylinder or bottle, with a wide 
mouth, to which a cork is fitted, as in 
Fig. 22. Cut a vertical notch in the 
cork to its center, and fix therein the 
stem of the seedling by packing with 
cotton. The cork thus serves as a 
support of the plant. Fill the jar 
with pure water to such a height 
that when the cork is brought to its 
place, the seed, S, shall be a little 
above the liquid. If the endosperm 
or cotyledons dip into the water, they will speedily 
mould and rot; they require, however, to be kept in 
