VITAL CHARACTERISTICS OF PLANTS. 175 



The microscopist sees proof of a higher life in plants than 

 he before conceived ; and he becomes convinced, after 

 examining the functions which their organs are destined 

 to perform, that animals and plants are only separate links 

 in the great chain of organic nature. 



The vegetable kingdom is divided into three great classes 

 the Dicotyledonous, or Exogenous plants, the Monocoty- 

 ledonous, or Endogenous plants, and the Acotyledonous, 

 Plants of the first and second classes bear flowers, and are 

 found in the temperate zones : those of the third do not 

 flower, and include the simplest forms of vegetable life, 

 being mostly found in warm climates. The characteristics 

 of exogenous plants, are first the branched or reticu- 

 lated veining of their leaves, next, the formation of their 

 stems, which consist of central pith, wood, and bark : 

 they increase in size by means of layers of new substance 

 every year deposited between the two latter. This mode of 

 growth gives to sections of their stems a ringed appear- 

 ance, the number of rings corresponding to the number of 

 years of growth. These rings are crossed at intervals by 

 straight lines, the medullary rays, which diverge from 

 the central pith, connecting them with the bark. 1 



Plants are organised beings ; that is, organisms com- 

 posed of a number of essential and mutually dependent 

 parts : in common, therefore, with animals, they possess 

 a principle which is in continued action ; and which 

 operates in such a manner, that the individual parts which 

 it forms in the body, are adapted to the designs of the 

 whole. Or, in more intelligible language, plants are living 

 bodies; like animals, they are the offspring of other beings 

 similar to themselves; they grow, are endowed with excita- 

 bility, have their periods of infancy, adult age, decay, and 

 death. Their affinity to animals is much closer than is 

 commonly supposed. The vital or creative power exists 

 already in the germ, in plants as well as in animals; and 

 by its influence the essential parts of the future plant are 

 formed. It might be supposed that the lateral generation 

 of plants namely, that renewal of the individual which 

 is the result of budding or gemmation is sufficient to dis- 



(I) See Dr. Lindley's Elements of Botany, for an excellent description of 

 vegetable structure; or Henfrey's Elementary Course of Botany. 



