210 ON PROP A GA TION B T SEED. 



40, and the most favourable temperature for germinating, Dr. Lindley 

 states to be for the seeds of cold countries, from 50 to 55 ; for 

 seeds of greenhouse-plants, from 60 to 65; and for seeds of the 

 plants of the torrid zone, 70 to 80. ('Theory of Hort.,' p. 166.) 

 It may be remarked that though the seeds of warm countries will not 

 vegetate in the temperature of cold countries, yet that the reverse of 

 this does not hold true, as may be observed in the germination of 

 British weeds in our stoves ; but the plants thus produced, unless im- 

 mediately removed to the open air, remain weak and sickly. 



The degree of heat which the seeds of plants will endure has already 

 been slightly noticed. Certain leguminous seeds, as those of some aca- 

 cias, may be subjected to the boiling point for a few minutes without 

 injury ; others may be allowed to steep and cool for twenty -four hours 

 in water heated to 200. The seeds of Acacia Lophantha were sub- 

 jected to boiling water for five minutes, and the plants raised from them 

 were exhibited before the Horticultural Society, some years ago, by Mr. 

 Palmer of Bromley, Kent. Messrs. Edwards and Colin found that 

 wheat, barley, and rye could germinate between 44 and 45 ; that 

 they were killed by remaining three days in water at the temperature 

 of 95; that in sand and earth, at 104, they lived for a, considerable 

 time; but that at 113 most of them perished; and that at 122 all of 

 them perished ; but it was found that a higher temperature could be 

 borne by these and other seeds for a shorter time. At 143, in 

 vapour, wheat, barley, kidney-beans, and flax retained their vitality 

 for a quarter of an hour; in dry air these seeds sustained no injury 

 at 167; but in vapour, at this temperature, they all perished. Dr. 

 Lindley mentions the very remarkable case of the germination of the 

 seeds of a raspberry, which had been picked from a jar of jam, and 

 which, consequently, must have been subjected to the temperature 

 of the boiling point of the syrup, which is 230. 



The degree of cold which seeds will endure differs according to the 

 species, their native country, and their condition in respect to moisture. 

 Dry seeds stand so high a degree of cold, that even the lowest tempera- 

 ture of the frigid zone does not injure them ; but if they have imbibed 

 any moisture they freeze according to the degree of growth which 

 may have been excited, and the degree of cold to which they had been 

 accustomed in their native zone. 



Atmospheric air is as necessary to the germination of seeds as 

 moisture and heat ; and this is the principal cause why seeds buried 

 to a certain depth in the soil do not vegetate. It also affords a reason 

 for having the surface of the soil, in which seeds are sown, porous, 

 and exposed to the action of the atmosphere, and to rain-water, which 

 contains more air than the water of wells. Hence the rapidity with 

 which seeds spring up in the open ground after the first warm spring 

 showers. Hence, also, the propriety of giving fresh air to hotbeds, 

 and to hand and bell-glasses covering sown seeds, even though they 

 have not come up. 



Bright light is found to be universally unfavourable ; because it has 

 a tendency to decompose carbonic acid, and fix carbon ; whereas, the 



