101 



cactuses and the prxkly pear are so constructed as to be great 

 water-storage structures, the "pseudo-bulbs" or swollen inter- 

 nodes of tropical epiphytic orchids are veritable water-bottles with 

 an extraordinary strong skin to prevent evaporation. With timber 

 the cells take on a spindle shape so that they can be compacted 

 together and resist transverse breakage ; while the cell-wall 

 becomes lignified with a modification of cellulose called " lignin." 

 Hence arises the great strength of wood to resist gravity and bear 

 a tree upright. One layer on the outer-side of the wood, called 

 the " cambium," remains in a state of active growth. This gives 

 rise to a new cylinder of wood annually, so that the age of trees 

 in this and most countries can be told by counting the cut ends 

 of the cylinders, looking like rings of wood in a transverse section 

 of a trunk of any timber tree. This, however, cannot be done 

 in a palm tree, as no cylinders of wood occur; all the woody 

 bundles, which collectively make a cylinder, are scattered about 

 in the general mass of cellular tissue. The cause of this has been 

 shown to be, without much, if any, doubt, an ancestral condition 

 of living an aquatic life. 



The principal parts played by carbon in vegetation have now 

 been passed in review, from its origin in carbonic acid gas to 

 its numerous final uses in the solid framework of all plants and 

 every part of it, and secondly the numerous carbonaceous pro- 

 ducts, each and all having some special use in plant life though 

 we cannot always discover what that use may be. 



Lastly, we have seen that when a hydro-carbon is destroyed 

 and resolved into carbonic acid and water, both being discharger! 

 into the air, the energy set free by the process enables the paint 

 to carry out all its functions and repeat the same processes ?s 

 long as it exists alive. 



III. 



Carbon from the Geographical Standpoint. 



By W. J. Woodhouse, A.C.P. 



(Read before the Geographical Section, March 25th, 1916.) 



"U^OR the third time I have the pleasure of addressing to' the 

 Geographical Section a lecture on some chemical element and 

 its relationship to geography. I have now to deal with carbon 

 along these lines. 



In my contributions on Silica and Calcium I dealt very largely 

 with the scenic effects and landscape pictures which are charac- 

 teristic of the presence of these elements, while the economical 

 branch of geography received a secondary position. In carbon I 

 am compelled to reverse this order, which will mean that the 

 topographical will take a second place, whilst the economic will 

 be of primary importance. 



