APPENDIX. 701 



temperature throughout the year than if it stood in the open sun ; consequently it 

 will always act as a condenser of moisture in the atmosphere that is in contact with 

 it. Thus, if a portion of wall is of the same temperature as the air, supposing 

 the latter to be within say 1 of saturation, the wall, with regard to the moisture it 

 may contain, will remain in nearly the same state ; increase the heat of the wall, 

 and it will give out moisture, and will ultimately become dry ; but render the wall 

 several degrees colder than the surrounding atmosphere, or lower than its dew 

 point, and, like the dew on the cooled bulb of Daniell's hygrometer, previously 

 explained, a deposition of moisture will immediately take place. This fact ought 

 to be borne in mind where dwelling-houses are to be erected in the proximity of 

 thick and lofty trees, or where trees of such description of growth are planted near 

 houses ; for if a row of trees are growing on the north sides of houses, the latter 

 are not in consequence affected by damp ; but if the houses are at the north side 

 of the tr\;es, nothing but strong fires, equal to the discrepancy of temperature occa- 

 sioned by a northern exposure, will render the houses equally dry ; and even in 

 this case, as the fire-heat cannot be made to pervade every part of the building, it 

 is probable a habitation in a northern exposure will not prove so healthy under 

 any circumstances as one otherwise situated. N. 



564, in p. 245. Substances yielding oxygen should be of most use in germination 

 to oily seeds, which have a deficiency of oxygen in themselves. 



571, in p. 248. According to Liebig, ammonia hastens and strengthens germi- 

 nation ; and, according to the same authority, charcoal and snow absorb ammonia 

 from the atmosphere ; this may be great part of the benefit. 



575, in p. 251. The plexus of vessels at the heel of the shoot or insertion of the 

 branch in the stem, causes a peculiar activity of life there ; and both buds and 

 roots are much more easily formed and in greater quantity there than in any other 

 place of the shoot. The insertion of the branch resembles in this respect the collar 

 of the stem (577). If the heel of the gooseberry or currant- cutting is taken out 

 completely by breaking off, not cutting, it is better than taking off a piece of the 

 old wood. 



578, in p. 252. Cuttings of growing succulent wood have vitality most active, 

 and strike root most quickly ; but, from the unripened state of the wood, are most 

 apt to die, and require to be kept more close and moist. There is danger in both 

 extremes, and both must be guarded against in such as are difficult to strike. 



580, in p. 253. When the season is hot and warm, and little time to attend to 

 keeping moist, succulent cuttings, such as pinks, are most certain to strike, by 

 paring close below the uppermost joint, and cutting off above close to the joint, 

 leaving none of the leaves uncut, except those beginning to develop. Such a cut- 

 ting is a mere joint in a vital, active, not ripened state, and will stand a great deal 

 of heat ; if covered with a hand-glass in sunny weather, or in a hotbed frame in 

 cold weather, they seldom or never fail. Excitement of heat, not preservation, is 

 all that is wanted. 



581, in p. 254. When cuttings are tardy to strike, and have callosities formed, 

 heat has a powerful effect in causing them to root. Those that have stood months, 

 without appearance of rooting, will strike in a few days in a strong heat 



601 in p. 262. The best mark for such as strike most readily by pieces of the 

 root is an abundance of thick viscid juice, as in the genera /Zhus, Papaver, Aildn- 

 tus, Gymndcladus, &c., which strike more freely than Cydonia, roses, thorns, &c.j 

 which have less. 



