62 ANATOMY AND PHYSIOLOGY OF 



Lichens, all the oi^gans of finctification are ahke, while in the moie 

 highly developed plants a contrast between these appears, a male 

 and female sex, the conjunction of which is necessary for the origin 

 of a new plant. 



Thus, the more complicated the structure of the entire plant 

 becomes, the more manifold the vital phenomena of the whole 

 display themselves, the more do we see the functions of the fun- 

 damental organs of the vegetable become restricted to an activity 

 continually becoming more special. The question here presents 

 itself: In what connexion does the more manifold or more special 

 activity of the cells stand with their organization ? To this ques- 

 tion we have no answer. The organization of cells, the substances 

 of which their membranes are composed, are so iiniform through- 

 out the whole vegetable kingdom, and all the organs of the par- 

 ticular plant, that as yet the connexion which must exist between 

 the form and organization, and the function of the cell, is alto- 

 e^ether unknown. 



The function of nutrition and that of propagation form a strik- 

 ing contrast in all the cases in which the propagation is by spores 

 and seeds, since the reproduction in these, through the germination 

 of an organ furnishing a new plant, always causes the death of 

 the organ of propagation, and in many eases of the whole plant. 

 But there is another kind of multiplication ; the propagation by 

 buds, which dependb on the common laws of growth, and has its 

 origin in the organs of vegetation. This mode of increase is 

 based on the peculiar growth of the plant. Leaving out of view 

 the simplest forms of the vegetable kingdom, the plant does not 

 consist of a fixed number of organs, developed together and at- 

 taining the full-growth at the same time, so as to form a com- 

 pleted whole, and to suffer a common death ; but the organs of 

 the plant are developed successively in an unlimited series ; every 

 fresh shoot has the strength of youth, and is capable, under fa- 

 vourable circumstances, of entering on an independent life sepa- 

 rately from the other parts, and of growing into a new plant. 

 When even all the parts of a plant do lead a common life, they 

 do not collectively form one individual, but separate individuals 

 growing out of each other, and blended together in consequence 

 of theix growth. It depends on the degree of organization of a 

 plant what part we are to regard as a special individual. When 

 an uni-cellular plant divides into two ceUs we must regard each 

 cell as an individual, e, g., in the Diatomeae ; in the Thallophy tes, 

 for instance in the Lichens, each lobe of the thallus can carry on 

 an independent life when separated from the rest of the plant ; in 

 the higher plants each branch forms a repetition of the stem which 

 grew from the seed, and a ramified plant is looked upon as a col- 

 lection of as many individuals as there are branches upon it. In 

 this manner a branched plant (when not exhausted by the pro- 

 duction of seed) is ever young in its fresh shoots, although one 



