CHAPTER I. 



PROPAGATION. 



Notwithstanding the close analogy that for the 

 most part exists between the natural economy 

 of animals and vegetables, there are some im- 

 portant points in which they widely differ, and in 

 none more so than in the means of their propa- 

 gation. AU vegetables were created for the sus- 

 tenance of animals ; and hence, wherever the 

 latter exist, the former are to be found. The 

 whole surface of the globe, whether covered with 

 water or not, is replete with vegetation, and that 

 vegetation exists not without its use. 



To supply the whole animal creation, it fol- 

 lows that vegetables must be not only exceed- 

 ingly numerous, but also readily produced — at 

 least, their means of production must be much 

 greater than that of animals themselves. Plants 

 not only produce immense quantities of seeds, 

 but they extend themselves by shoots which run 

 on or under the ground ; they are capable of 

 multiplying themselves by roots, tubers, and 

 bulbs, both formed under ground, and in some 

 cases on the leaves and stems ; and they produce 

 innumerable buds, each of which, by human art, 

 can be rendered equivalent to a seed, and hence 

 the great facility by which plants are multiplied 

 both by nature and art. 



It is probable that something like one hundred 

 thousand species of plants exist ; the herbaria of 

 some botanists contain nearly that number in 

 dried specimens. Thirty thousand seven hun- 

 dred species are enumerated as indigenous or 

 cultivated in Britain alone ; and if we include 

 the botanical varieties, and those of cultivated 

 vegetables, fruits, roses, and florists' flowers, 

 eleven or twelve thousand may be added. 



§ 1. PROPAGATION BY SEED. 



Propagation by seed is the primary and most 

 general process by which plants are multiplied 

 and perpetuated, AU plants are so produced, 

 although in many, such as ferns, mosses, algse, 

 and fungi, the seeds are so small as to be invisible 

 to the naked eye; yet these latter are amongst the 

 most widely diffused of all vegetables. The seeds 

 of the latter are dispersed by a variety of means, 

 by atmospheric and other causes, their minute- 

 ness and buoyancy adapting them well for aerial 

 distribution. There is scarcely a point on the 

 globe's surface, or even in the ocean's depths, 

 VOL. II. 



where they are not found to exist : the whole 

 atmosphere seems to be replete with them ; and 

 when they are brought into contact with solid 

 bodies forming a proper nidus for them, there 

 they take root and flourish. Nor are the plants 

 originated from such apparently slender means 

 proportionably minute; many of them attain 

 an almost gigantic size, as exempHfied ia many 

 of the Algae, whose ramified branches extend to 

 the length of hundreds of feet, while the tree 

 ferns rank amongst the monarchs in the tropical 

 forests. 



The powers of reproduction by seed are truly 

 immense : a single capsule of the tobacco plant 

 contains about one thousand seeds ; one of the 

 common medicinal poppy, eight thousand; while 

 the vanilla plant has been computed to contain 

 from ten to fifteen thousand. Each of these, 

 upon a very moderate calculation, produces from 

 twenty to thirty capsules on each plant. To give 

 some idea of the powers of reproduction amongst 

 cryptogamous plants, we may state that a single 

 frond or leaf of the common spleenwort is esti- 

 mated to produce one mUliou of seeds. 



Most plants originated from seeds resemble 

 their parents in a very striking degree, although, 

 occasionally, deviations of greater or lesser im- 

 portance occur ; hence many of our most valu- 

 able plants, and especially fruits and culinary 

 vegetables, have so originated, and when suffi- 

 ciently marked by symptoms of improvement, 

 are denominated varieties. 



All vegetable life commences from seed. Its 

 first stage and after progress are thus described 

 by Dr Lindley in " Introduction to Botany :" 

 " If we place a seed in earth at the temperature 

 of 32° Fahr., it wiU remain inactive till it finally 

 decays ; but if it is placed in moist earth above 

 the temperature of 32°, and screened from the 

 action of Ught, its integument gradually imbibes 

 moisture and swells, oxygen is absorbed, carbonic 

 acid expelled, and the vital action of the embryo 

 commences. It elongates downwards by the 

 radicle, and upwards by the cotyledons, the 

 former penetrating the soil, the latter elevating 

 themselves above it, acquiring a green colour by 

 the deposition of carbon absorbed from the at- 

 mosphere in the light, and unfolding in the form 

 of two opposite roundish leaves. This is the 

 first stage of vegetation. The young plant con- 

 sists of little more than cellular tissue, only an 



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