HORTICULTURAL JOURNAL. 171 



Candolle, 'Physiologie Vegetale,' ii. 984), that the} 7 have no internal cause 

 for death, but I believe incorrectly. Examples of very old trees, such as 

 De Caxdollr collected («. g. Taxus 3000, Adansonia 5000, Taxodium 6000 

 years old, &c.,) only prove, naturally, that death occurs a.t a very late period 

 in many plants placed in favourable circumstances, but sot that it does not 

 necessarily happen. To me there appears to exist m all trees, whether they 

 belong to the Dicotyledons, -or, like the Palms, to the Monocotyledons, an 

 internal cause which must produce death in time — namely, the increasing 

 difficulty of conveying the necessary quantity of nourishment to the vegata- 

 ting point, resulting fivom the elongation of the trunk from year to year. 

 Even when the force which carries the sap up suffices to raise it to 200 feet 

 or more (many Palms, as Ceroxylon andicola, Ar-eea oleracea, attain a height 

 of 150 — 180 feet ; some Coniferse, e. g., Pinus Lambertii, Abies Douglasii, 

 of more than 200 feet), yet a maximum is reached there, and the terminal 

 shoot is less perfectly nourished every succeeding year, becomes stunted 

 more and more, and the tree at length dies. 



" 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 or- 

 gan 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 development, but also 

 the food on which the entire animal kingdom depends. But plants not only 

 nourish animals, they maintain the air in a fit state for their respiration, 

 since their breathing process removes carbonic acid from the atmosphere and 

 replaces it by oxygen gas. 



" In all these functions the plant is thoroughly dependant upon the outer 

 world ; its food is brought to it without its own co-operation, by water and 

 air ; its respiration takes place without activity of its own, through a pene. 

 tration 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 de- 

 pend on a mechanical activity of a circulating 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 vegetable kingdom, 

 are also altogether of subordinate kind in the individual plant. They also are 

 c ommitted to the cells. ****** 



"Thousands of experiments," ( says Professor Mohl,) "have shown that 

 the young shoots of old trees, when used as grafts, slips, &c, furnish as 

 strong plants a3 the shoots of young trees; even in the Palms ( Phoenix 



& 



