GER 



247 



GER 



A certain degree of warmth is essen- that prevent the incubation of egps, un- 

 ti.il ; for no known plant has seed that ' less they be kept for a certain period at 

 ■will germinate below or at the freezing ', a temperature of about lOC^ 



point of water. A temperature above 

 32o of Fahrenheit's thermometer there^ 



As no seed will germinate unless a 

 certain degree of heat is present, so also 



fore is requisite. But on the other hand, does it require that a certain quantity 

 the temperature must not be excessively of water is in contact with its outer 

 high. Even no tropical seed, probably, skin or integument ; and this is required 

 will germinate at a temperature much not only to soften this covering, and 

 above 120^ F., and we know from the thus permit the enlargement of the co- 

 experiments of M. M. Edwards and tyledons (seed lobes) always preceding 

 Colin, that neither wheat, oats, nor bar- | germination, but also to aftord that wa- 

 ley will vegetate in a temperature of ter to internal components of the seed. 



113' 



without which the chemical changes 



Every seed differing in its degree of necessary for the nutriment of the em 



excitability, conseqbently, has a te 



seqbe 

 t wlii 



perature without wliich it will not ve- 



bryo plant will not take place. As 

 water is essential to germination, and 



getate, and from which cause arise the only a certain quantity is required for 

 consequences that dirterent plants re- ; its healthy progress, so is it by no means 

 quire to be sown at different seasons, a matter of indifference what matters it 

 and that they germinate with various I holds in solution. Until germination 

 degrees of rapidity. The gardener has commenced, no liquid but water at 

 should always bear in mind that it would common temperatures will pass through 

 be a very erroneous conclusion, because the integuments of a seed. 

 a seed does not germinate at the accus- : So soon as germination has com- 

 tomed time, that therefore its vegetating menced, this power to exclude foreign 

 powers are departed. No two seeds fluids ceases ; but the organs starting 

 taken from the same seed-vessel ger- i into activity, the radicle and the plumule 

 minate precisely at the same time; but \ are so delicate, that the weakest saline 

 on the contrary, one will often do so I solutions are too acrid and ofiensive f'»r 

 promptly, while its companion seed will them. It may be noted as a warning to 

 remain dormant until another year. those who employ steeps for seed, with 



M. de Candolle relates an instance the hope of promoting the vigour of the 

 where fresh tobacco seedlingscontinued , future plant, that they must keep the 

 to appear annually for ten years on the seed in those steeps a very few hour?, 

 same plot, though no seed was sown In forty-eight hours, if the temperature 

 after the first sowing; and the same ' be 60° or more, putrefaction coin- 

 phenomenon usually occurs for two or inences, and germintition is weakened, 

 three years, when the seed of either the or entirely destroyed. M. Vogcl, of 

 peony or hawthorn are sown. Why one Munich, has published an exieiuied 

 seed is more easily excited than another course of experiments upon this subject, 

 is as yet unexplained ; but the wisdom and they fully confirm my opinion that 

 of this one of many i)rovisions for avoid- salts, innoxious when the plant is of 

 ing the accidental extinction of a spe- robust and advanced growth, are fatal 

 cies in any given locality is readily dis- to it at the lime of germination. 

 cerned. An ungenial spring may destroy : The presence of one of the conslito- 

 the plants from those seeds which first ent gases of the atmosphere, oxygen, is 

 germinated; but this could scarcely oc- also essential to germination. It is ne- 

 curalso to those of the second and third cessary that the oxygen should penetrate 

 year, or even to those which were only \ to the cotyledonous parts of the seed, 

 a few weeks later in their vegetation. as is evident by the changes which take 



It is not possible to enunciate a ge- place during germination, and it is f\ir- 

 neral rule relative to germinating teni- ther proved by experiment. Wtien 

 peratures, requiring no exceptions; but healthy seed is moistened and exposed 

 in general, for the seeds of plants, in a suitable temperature to atmos- 

 natives of temperate latitudes, the best pheric air, it absorbs the oxygen only, 

 germinating temperature is about 60°, This power of separating one gas froi.i 

 and for those of tropical plants about the others appears to reside in tlie 

 80°; and the necessity for such tempe- , integuments of the seed, for old seeds 

 ratures depends upon the same causes ; lose the power of absorbing the oxygen, 



