PLANTING. 19 



fitted to imbibe air and moisture. The essential constituents of atmos- 

 pherical air are oxygen and nitrogen or azote ; and it holds in solution car- 

 bonic acid gas and water; they are elastic and invisible, but can be 

 separaled from each other, and their bulk, or volume, and weight can be 

 determined, and their properties satisfactorily ascertained*. Oxygen 

 has received the name of pure or vital air, because animals cannot respire 

 if the air they breathe be deprived of it, nor can seeds vegetate unless it 

 be present in the soil and air in which they are placed. It enters into 

 the composition of the vegetable and most other acids, and largely into 

 that of sugar and extract. It forms about one-fifth of the air of the 

 atmosphere. Carbonic acid gas constitutes about a thousandth part of 

 atmospherical air, its basis carbon is well known in the state of charcoal, 

 and is the fundamental constituent of wood. Nitrogen, or azote, con- 

 stitutes about four-fifths of the atmospherical air. Its offices have not 

 been so clearly discovered : with much reason, however, it appears to be 

 employed in the formation of several products of vegetation, as gluten and 

 albumen, and in modifying the actions of the other components of the 

 air. It is remarkable that carbonic acid gas being so largely produced 

 by numerous artificial and natural processes constantly going on, as in the 

 putrefaction of substances of every kind, in fermentation, combustion, 

 respiration of animals, and, during darkness, by the green system of the 

 whole vegetable kingdom, so small a portion only of it should be found 

 permanent in the air, varying from -jfa to T^TT P art as tne minimum and 

 maximum. It is heavier than the other constituents of air, and it is lost 

 from the atmosphere, or from wherever it may exist in plants only, and 

 forms the bulk or basis of every kind of wood ; it must be at pre- 

 sent considered as being largely taken up by the roots of plants. Water, 

 the last mentioned constituent of atmospheric air, enters into it in the 

 state of vapour. The quantity of it suspended in the air is supposed to 



* The elasticity of the constituents of atmospheric air is so powerful, that when, from 

 local causes, one ingredient is generated in undue proportion to the others, the most perfect 

 analysis of the general air in the immediate neighbourhood of the spot where this circum- 

 stance happens cannot detect any difference in the proportions of the proper constituents 

 from that of the air of the most healthy region. The atmosphere of a crowded city and 

 that of an open or moderately sheltered alpine region, afford by analysis the like number and 

 proportion of ingredients or elements ; but notwithstanding this, the influence of the air 

 of these two situations on vegetation is very different. There are certain plants which 

 will not grow in the atmosphere of a crowded city, and there are others which thrive in the 

 former, and will not continue long in that of an alpine air. Some of the following plants 

 grow freely in the atmosphere of the crowded parts of the city of London. 



Plants that grow freely. Plants that exist for only a few years in perfect health. 



Sycamore. Laburnum. 



Elms. 



Mulberries That exist in health only a limited time. 



Ivies Privets 



Virginian Creepers China Roses 



Vines Alpine Plants, scarcely ever produce 



Oriental Planes, bulbous and tuberous- flowers, 



rooted plants, except Snowdrops. 



Since the above list was written, the Bedford Conservatory, or new flower and plant 

 market, Covent Garden, London, has been erected by John Duke of Bedford, and this 

 interesting feature to the ornament of the metropolis will afford extensive means to 

 determine what species of hardy as well as of tender plants will thrive in the atmosphere of 

 so large and crowded a city as that of London. Since this part of the market was com- 

 pleted in the month of June last year, the following plants may be mentioned as having 

 thriven best. The orange, Citrus aitranlium; camellia, Camellia Japonica; rhododendrons, 

 R. ponticum, R. maximum, R. punctatum. Some kinds of pelargoniums, Geranaceee. 

 Heaths, particularly Erica tubijlora, E. cylindrica, E. persoluta, E. cupressina, E. odora- 

 rosa / Acacia verticillnta } A. armata } Epachris grandiflora } E~, pungens rosed. 



C 2 



