Qi ANATOMY AND PHYSIOLOGY OF 



Fmus Zamhertiij Abies Dauglmii, of more tliaii 200 feefc)^ yet a maximum 

 is reached tliere, and the terminal shoot is less perfectly nourished every 

 succeeding year^ becomes stunted more and more, and the tree at length 

 dies. 



Thousands of experiments have shewn that the young shoots of old 

 treesj when used as grafts, slips, <fec., furnish as strong plants as the shoots 

 of young trees; even in the Palms (Flimnix dactylifera) experiment has 

 shewn that the apex of the stem, when its vegetation begins to slacken 

 in an old tree, grows again into a strong tree when cut off and planted in 

 the earth. ISTot one single experiment speaks in favour of the opinion 

 promulgated by Knight, that all parts of a tree have a common end to 

 their life, and that the different trees which have been raised from one 

 and the same tree by grafts, decay about the same time as the parent 

 plant. A whole series of cultivated plants (I will only mention the 

 Yine, the Hop, the Italian Poplar, and the Weeping Willow) are propa- 

 gated by division, without any decreased power of vegetation ever being 

 seen. Nothing was in greater contradiction to the laws of vegetable life, 

 than the frequently expressed opinion, that the Potato disease of recent 

 years was to be ascribed to a degeneration of the Potato plant, arising 

 from the unceasing propagation by tubers. 



If we are surprised at the intensity of the vegetative force of 

 individual plants, in consequence of which it re-appears with new, 

 unweakened energy in every bud, so must we marvel at the force 

 committed to so simple an organ as a cell is, if we reflect what 

 an influence it exerts upon the total economy of nature, as one of 

 the grandest of phenomena. The plant lives almost solely upon 

 inorganic substances ; its cells are chemical laboratories in which 

 these are combined into organic compounds. The plant prepares 

 in this way not only the nutriment required for its own develop- 

 ment, but also the food on which the entire animal kingdom de- 

 pends. But plants not only nourish animals, they maintain the 

 air in a fit state for their respiration, since their breathing process 

 removes carbomc acid from the atmosphere and replaces it by 

 oxygen gas. 



In all these functions the plant is throughly dependant upon 

 the outer world; its food is brought to it without its own co-opera- 

 tion, by water and air ; its respiration takes place without activity 

 of its own, through a penetration of its substance by gases with 

 which it is in contact, in consequence of a physical law ; not even 

 does its internal circulation of juices depend on a mechanical 

 activity of a circulatiag system ] thus every necessity for motion 

 is removed. It is true we here and there meet with movements 

 in this or that organ, but these, occurring isolated in the vege- 

 table kingdom, are also altogether of subordinate kind in the 

 individual plant. They also are committed to the cells. 



