418 Neio Forcing-houses and Pits, 



exactly alike ; and some will occasionally differ considerably from 

 all the rest. Nevertheless, it is an undoubted fact, that all seed- 

 ling plants not only possess the character of the species from 

 which they have sprung, but even, in by far the greater number 

 of cases, some of the pecuHarities of the individual. The seeds 

 of any kind of cultivated apple, for example, will produce plants, 

 the fruit of all of which will more or less resemble that of the 

 parent ; though perhaps some one or two among a hundred may 

 be considerably different. Hence, by selecting from beds of 

 seedling plants those which are in any way remarkably different 

 from the rest, new varieties are procured ; and, till within the 

 last half century (when artificial cross-breeding began to be prac- 

 tised by gardeners), this was the only way in which an improved 

 variety of any species of plant was procured. 



Plants, like animals, are subject to various diseases, as well 

 as to be preyed on by insects, most of which live on plants till 

 they have completed their larva state. Plants are also in- 

 jured by being crowded by other plants, either of the same or 

 of different species. When these spring up naturally around 

 the cultivated plants, they are called weeds, and the cultivated 

 plant is cleaned from them by weeding; as it is in the case of 

 being crowded by its own species, or by other cultivated plants, 

 by thinning. Plants are also injured by epiphytes, which grow 

 on their outer bark, such as mosses and lichens ; and by para- 

 sites, which root into their living stems and branches, such as 

 the dodder, mistletoe, &c. 



The life of plants, like that of animals, is limited, but varies 

 in regard to duration. Some plants vegetate, flower, ripen seed, 

 and die, in the course of a few months, and these are called an- 

 nuals; while others, such as the oak and some other trees, are 

 known to live upwards of a thousand years. In both plants and 

 animals, decay commences the moment the life is extinct; and 

 in both they are ultimately resolved, first, into a pulpy or other 

 homogeneous mass, for manures, and ultimately into certain 

 gases, salts, and earths. After death, the decay both of animals 

 and plants may be retarded by the same means ; viz. drying, 

 exclusion from the air, or saturating with saline or antiseptic 

 substances. 



Hampstead, Juli/, 1838. 



Art. III. Notice of some new Forcing-houses and Pits, lately erected 

 at PendarveS) in CorJiwall ; "with a Plan and Section. By J. Mit- 



CHINSON. 



I SEND herewith plans and sections of some new forcing- 

 houses and pits lately built here, which, I think, may be useful 

 to some of the readers of the Gardener's Magazine. 



