GEOGRAPHICAL DISTRIBUTION OF PLANTS. 



37 



vitality for ten or twelve years. Melon and Cucumber seeds, which are 

 mucilaginous, may be kept for thirty or forty years; Kidney-beans for nearly 

 a century ; but not Scarlet Runners, which will not keep above two years ; 

 a remarkable circumstance, since the two species are so nearly allied as to 

 be considered by some to be only varieties. The seeds of many Legumindsae, 

 and particularly those of warm climates, where their carbon is concentrated 

 to the hardness even of wood, as in the Australian Acacias, will keep an 

 unknown period ; as a proof of which, all France continues 'to be supplied 

 with seeds of the common Sensitive Plant from a bag which was sent to 

 Paris, we believe, above sixty years ago. In general the younger and 

 more vigorous the seed, the stronger will be the plant produced, and 

 the contrary. Hence when it is wished to have plants of a vigorous- 

 growing species, of more concentrated growth than usual, seeds weaker 

 from being smaller and less abundantly nourished, or from being dried 

 by long keeping, are chosen ; and when very vigorous plants are desired, 

 the largest and freshest seeds are selected. Thus in the case of plants pro- 

 ducing their flowers in corymbs, the seed is chosen from the summit of the 

 corymb, as the first flowers open there, which, as well as the seeds which 

 follow them, are always the largest. In general the first-formed flowers of 

 all plants are the strongest, and the seeds produced by them the largest and 

 most vigorous of growth. 



133. In this section there is necessarily some repetitions of facts stated in 

 preceding parts of this chapter ; but it became necessary to do so in order to 

 connect the process of development with structure. The reader who is de- 

 sirous of studying the subject more in detail is recommended to consult 

 Lindleys Principles of Horticulture^ and Lymburn, Beaton, and Niven, in 

 the Gardeners Magazine ; from which source, and our own observation and 

 experience, this section has been chiefly compiled. 



Sect. VI. — The Geographical Distribution of Plants^ and their Stations and 

 Habitations, with reference to their Culture in Gardens. 

 184. By the geography of a plant is to be understood the latitude and 

 longitude in which it abounds in a wild state ; by its station or " habitat," 

 the particular soil or situation in which it is found ; and by its habitation, 

 the particular range of country to which it is limited. In a general view, 

 the vegetation of the globe is distributed over its surface, varied according 

 to its latitude, its inequalities of elevation, and its differences in regard to 

 soils and moisture. The subject is of great importance to gardeners, because 

 the culture of all plants must necessarily be more or less founded on a know- 

 ledge of the climate and station in which they are found wild. In the 

 natural distribution of plants on the earth's surface, the different species 

 are found only in particular situations, which they prefer to others. Some 

 prefer exposure to the full influence of the light and air ; others the shade 

 of rocks or of trees ; some grow on mountains, some in plains, some in bogs 

 or marshes, some on the banks of rivers ; some in the running water of 

 rivers, others in the still water of lakes ; some in salt marshes, and others 

 in the sea. Each of these different localities, in any one country, is charac - 

 terised by a difference in physical circumstances; such as more or less 

 elevation above the level of the sea ; a greater or less exposure to light ; a 

 soil more or less compact in texture ; abounding more or less in water ; or 

 composed of particular earths. All this is independent of temperature, 



