OUTLINES OF THE VEGETABLE KINGDOM. 117 



tions, and possess homologous vital properties. The phenomena of 

 nutrition and reproduction, and the property of contractility giving 

 rise to motion, are manifested in, or possessed by, all animals ; sensa- 

 tion and voluntary motion in most. Experimental physiology rests 

 upon this fundamental unity of functions as well as of plan; and rec- 

 ognizing the resemblances, whilst allowing for the differences, between 

 man and the lower animals, it has succeeded in eliciting many impor- 

 tant physiological facts arid doctrines, which illustrate the functions of 

 the human body, more especially, it may be added, those of the various 

 parts of the nervous system. 



Due consideration being given to all the preceding facts, to the 

 small number of typical plans of animals, to their known modifications 

 or variations, on the one hand, and to their mutual points of approxi- 

 mation or alliance on the other, and especially to the higher laws of 

 homology and form, a certain "unity" is seen to be manifested 

 amidst all the "variety" which prevails ; and more or less broken, yet 

 gradational, lines can be traced through the animal series. 



In conclusion, it may be remarked that the profound study of the 

 entire chain of homologies connecting animals of the same type with 

 each other, has led to the opinion of the existence of certain still more 

 intimate relations between them, viz., those of a genetic kind, extend- 

 ing through vast periods of time, and expressed in the formula of con- 

 tinuous "descent with modification." The possibility of such genetic 

 relations has even been surmised in regard to animals of the different 

 types, and they have likewise been supposed to include man himself, 

 considered as the highest existing animal form upon the earth. 



RELATIONS OF MAN AND ANIMALS WITH PLANTS. RELATIONS OF 

 THE ANIMAL AND VEGETABLE KINGDOMS. 



Besides the more intimate relations which exist between man and 

 animals, and between animals themselves, there are other and highly 

 important relations between the animal kingdom, man inclusive, and 

 the vegetable kingdom ; these relations are of three kinds, viz., of 

 resemblance, difference, and dependence. To explain them, it is nec- 

 essary to give some preliminary information concerning the vegetable 

 kingdom. 



Outlines of the Vegetable Kingdom. 



Classification. By Linnseus, plants were divided into the Phanerogamia or 

 Flowering plants, and the Cryptogamia or Flowerless plants ; but by Jussieu 

 and the followers of the Natural system, a tripartite classification has been 

 adopted into Dicotyledonous, Monocotyledonous, and Acotyledonous plants ; the 

 two former together corresponding with the Phanerogamia, and the latter 

 with the Cryptogamia. 



The Dicotyledona include the most highly developed forms in the vegetable 

 world ; they all produce true leaves, flowers, and seeds ; they are so called 

 because the seed possesses two seed-lobes or cotyledons, which, when developed 

 in germination, form two little embryonic leaves. The stems of these plants 

 are formed by the regular growth of new concentric layers of vascular and 

 woody tissue deposited in succession one outside the other, the earliest formed 

 layer immediately surrounding the central soft part called the pith, and the 

 latest formed layer being that placed immediately beneath the cuticle or bark ; 



