CONDITIONS FOR THE GROWTH OF PLANTS. 29 



under verdurous domes, in the bosom of these vast wilds, are 

 the only paths that nature has opened to the scattered inhabi- 

 tants of these rich solitudes. Elsewhere, in Mexico and Yu- 

 catan, an invading vegetation permits not even the works of 

 man to exist ; and the monuments of a civilization compara- 

 tively ancient, which the antiquary goes to investigate with 

 care, are soon changed into a mountain of verdure, or demol- 

 ished, stone after stone, by the plants piercing into their 

 chinks, pushing aside with vigor, and breaking with irresisti- 

 ble force, all the obstacles that oppose their rapid growth." 



The author, in his " Elements of Physical Geog- 

 raphy," * page 119, thus refers to the growth of 

 living matter : 



" All life, whether vegetable or animal, consists of various 

 groupings of cells, or approximately spherical masses, con- 

 sisting of a peculiar form of a jelly-like matter called proto- 

 plasm, composed of various complex combinations of carbon, 

 hydrogen, oxygen, and sulphur, called proteids. At its begin- 

 ning all life consists of a minute germ-cell, filled with more 

 or less transparent protoplasm, and containing a darker 

 opaque spot called the nucleus. Examined by a sufficiently 

 powerful glass, all living protoplasm is seen to be in constant 

 motion, currents passing through the different parts in some- 

 what definite directions. 



* Eeprinted, by permission, from " The Elements of Physical 

 Geography, for the Use of Schools, Academies, and Colleges." 

 By Edwin J. Houston, A.M. Eldredge & Brother, No. 17 

 North Seventh Street, Philadelphia. 1891. Pp. 272. 



3* 



