246 ON PROPAGATION BY SEED. 



ground, had not strength to free themselves from the soil. In 1830, how- 

 ever, after being damped, I added quicklime in the state of powder, which, 

 besides furnishing an alkali, has a great affinity for carbonic acid, which is 

 necessary to be extracted from the starch before it can be made soluble, and 

 which produces heat by concentration of the oxygen and carbon when being 

 extracted. After the seed was thoroughly damped, I sprinkled it with the 

 powder of lime, and kept it damp by the use of a watering- pan, for ten or 

 twelve days ; at the end of which time it had swelled off plump, and had all 

 the sweet smell of the sugar formed in healthy seed when malted in this way : 

 and, when deposited in the ground, it was not long in pushing up its seed 

 leaves, as healthy, upright, and dark green hi the colour, as the first year it 

 was sown ; and the seedling plants were strong and healthy. The reasons 

 why I preferred lime were, its cheapness, and the affinity of quicklime for 

 carbonic acid : as to its alkaline properties, soda is much more powerful, but 

 lime seemed to be that which had produced most effect in the experiments 

 of M. Payen and others on the same subject. The seed must be carefully 

 kept damp till sown, as the dry powder is apt to corrode ; and seeds do not 

 suit well to have their dormant powers brought into action without being 

 sustained, which, if far forward and severely checked, may destroy life alto- 

 gether. Since I experimented as above on the spruce fir seed, I have not had 

 any other seed so long kept to make trial of; I have, however, tried lime on 

 magnolias and other weak-growing seeds difficult to start, and found them to 

 germinate sooner, and make stronger plants than usual. Some others who 

 have tried it have also found it of benefit. It is to seeds containing their 

 albumen principally in the form of starch, that it will be of most benefit ; 

 and to those which have been hurt by long keeping dry, or being exposed to 

 great heat : those which have been spoiled by dampness have their food de- 

 composed and spoiled. It is difficult, also, to say how far the drying can be 

 endured without being prejudicial, and when the organised tissue, the seat of 

 life, may have its powers of resuming vital activity so far trenched on as to 

 be considered dead. After this has taken place, any stimulus that can be 

 applied can only hasten consumption, as the vital force which should preside 

 over and direct the chemical force has fled." (Gard. Mag. for 1841, p. 520.) 



566. The length of time during which seeds retain their vitality varies ex- 

 ceedingly in different species ; and the difference in this respect, even in the 

 plants in common cultivation, as every seedsman knows, is very considerable. 

 It is remarkable that the seeds of annual plants not only germinate in general 

 quicker and with more certainty than those of perennials, but, also, that 

 they retain their power of germination much longer. The greater part of 

 the seeds of perennial plants and trees, when well kept, preserve their germi- 

 nating powers for a long time; while certain oily seeds, like those of 

 dictamus, magnolia, and myristica, &c., decay soon after ripening. Melon 

 seeds have been known to retain their vitality for nearly half a century, 

 kidney-beans for a century, and the seeds of the sensitive-plant upwards of 

 sixty years. 



567. The length of time that seeds will lie in the ground without growing, 

 is not less remarkable than the difference in their retention of vitality. 

 Many seeds, which, when sown in spring, come up soon afterwards, will not 

 come up the same year if sown in autumn. This is the case with many 

 common annuals, which when sown immediately after ripening either do 

 not come up at all that year, or come up sparingly and sickly, In May 



