INFLUENCE OF WATER AND HEAT UPON GERMINATION. 15 



In addition to this, the absorption of water causes all the 

 parts to soften and expand; many of the dry, but soluble, 

 parts to become fluid ; sap, or vegetable blood, to be formed ; 

 and a motion of fluids to be established, by means of which 

 a communication is maintained between the more remote parts 

 of the embryo. 



Heat seems to set the vital principle in action, to expand the 

 air contained in the numerous microscopic cavities of the seed, 

 and to produce a distension of all the organic parts, which thus 

 have their irritability excited, never again to be destroyed 

 except with death. What degree of heat seeds find most 

 conducive to their germination, probably varies in different 

 species. Chickweed (Stellaria media) and Groundsel (Senecio 

 vulgaris) will germinate at a temperature but little above 

 33° Fahr. 



It has been imagined that electbicai action also promotes the 

 germination of seeds. Sir H. Davy found that seeds placed in the 

 vicinity of the positive pole of a voltaic pUe, germinated sooner than 

 those near the negative pole ; and judging from the known powers of 

 electricity it was not unreasonable to expect, that, Kke light and heat, 

 it would exert influence on the growth of vegetables. Professor 

 Edward SoUy, however, has shown, experimentally, by an extensive 

 series of trials in the Garden of the Horticultuial Society, that this is 

 not so. Seeds of Barley, Wheat, Rye, Turnip, and Radish, were, in 

 several different experiments, found to germinate with increased 

 rapidity, when exposed,to the influence of a feeble current of electricity 

 of very low tension, and the plants not only came up sooner, but were 

 more healthy than others; but, on the other hand, a number of 

 experiments on other seeds had given quite opposite results, proving 

 either that the germination of some seeds was retarded, whilst that of 

 others was facilitated, by electricity ; or, that the effects, observed in 

 both cases, were merely accidental. Out of a series of ftfty-five 

 experiments on different seeds, twenty appeared in favour of electricity, 

 ten against it, and twenty-five showed no effect whatever; and, on 

 oarefoily counting the whole number of seeds up in the entire series, it 

 was found that twelve hundred and fifty of the electrified, and twelve 

 hundred and fifty-three of the non-electrified seeds had grown. 



Germination being established, by the absorption and decom- 

 position of water, and by the requisite elevation of temperature, 

 all the parts enlarge, and new parts are created, at the expense 



