THE ASH OF PLANTS. 



]81 



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 im- 

 mersed in water, containing in solution or suspension the 

 substances whose action was to be observed. 



Water-Culture 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 prop- 

 erly given in this place. Cause a num- 

 ber of seeds of the plant it is desired to 

 experiment upon to germinate in moist 

 blotting-paper, 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 vnth 

 cotton.. The cork thus serves as a sup- 

 port 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 a moist atmosphere. Thus arranged, suitable 

 warmth, ventilation, and illumination alone are requi- 

 site to continue the growth until the nutriment of the seed 



Fig. 38. 



