3 2 SEED-SOWING. 



producing heat ; the oxygen, therefore, which has penetrated 

 the tissues is sufficiently heated to cause oxidation, and the 

 consequent awakening of vegetable life. According to the 

 experiments of MM. Dehe'ian and Landrin, the condensation of 

 the gases in the seed is the first commencement of germination. 

 If this condition is not produced, whether from want of water 

 or because the air cannot reach the seed, there can be no for- 

 mation of the immediate principles necessary for the evolution 

 of the germ. These experiments, although highly scientific, 

 are very interesting from a practical point of view, as they 

 enable the cultivator to determine the influence which the 

 solidity of the soil, the dryness or the excess of moisture, 

 the depth of earth in which the seed is placed, may have 

 on the success of the sowing. Experience has already taught 

 us much on these matters ; but scientific methods, corro- 

 borating as they do the observations of practical men, can 

 alone point out the sure means to be employed to bring about 

 desired results. 



A weak solution of alkali quickens the growth of some seeds, 

 and lime-water has been recommended as a steep for cereals, 

 coniferous, and other seeds ; but it must be used in a weak 

 state. The secret of success in using lime would seem to be 

 its affinity for carbonic acid, which it extracts from the seed, 

 and thus induces a more rapid germination than the application 

 of heat and moisture alone. Humboldt employed a weak 

 solution of chlorine, which possesses the power of decomposing 

 water, and thus setting oxygen at liberty ; and diluted oxalic 

 acid has been successfully used in the case of very old seeds. 

 Camphor has long been said to possess the property of hasten- 

 ing the germination of seeds, and similar properties have been 

 attributed to bromine, chlorine, and iodine. M. Heckel has 

 recently experimented with these substances, and the results go 

 towards proving the correctness of this assertion. Radish- 

 seeds, simply moistened with pure water, germinated in eight 

 days ; similar seeds, kept moist with iodine water, germinated 

 in five days, with bromine water in three days, and with chlo- 

 rine water in two days. The monobromide of camphor 

 exhibited even greater quickening energy than either of its 

 constituents used separately, or than a simple mixture of 

 bromide and camphor, germination occurring after a mean 

 interval of thirty-six hours. Alkaline borates and silicates, on 

 the other hand, were found to retard germination, even when 

 used in relatively small proportions ; stronger solutions checking 

 germination for an indefinite period. Arsenious acid and the 



