C 31 ] 



to make the plats deviate a very little from the per- 

 pendicular. Where horizontal layers are pushed 

 forth, as in certain grasses, particularly such as the 

 fiorin, lately brought into notice by Dr. Richardson, 

 more food may, however, be produced upon an irre- 

 gular surface ; but the principle seems to apply strict- 

 ly to corn crops. 



The direction of the radicles and germens is such 

 that both are supplied with food, and acted upon by 

 those external agents which are necessary for their 

 developement and growth. The roots come in con- 

 tact with the fluids in the ground ; the leaves are ex- 

 posed to light and air ; and the same grand law which 

 preserves the planets in their orbits, is thus essential 

 to the functions of vegetable life. 



When two pieces of polished glass are pressed 

 together they adhere to each other, and it requires 

 some force to separate them. This is said to depend 

 upon the attraction of cohesion. The same attraction 

 gives the globular form to drops of water, and enables 

 fluids to rise in capillary tubes ; and hence it is some- 

 times called capillary attraction. This attraction, like 

 gravitation, seems common to all matter, and may be 

 a modification of the same general force ; like gravi- 

 tation, it is of great importance in vegetation. It pre- 

 serves the forms of aggregation of the parts of plants., 

 and it seems to be a principal cause of the absorption 

 of fluids by their roots. 



If some pure magnesia, the calcined magnesia of 

 druggists, be thrown into distilled vinegar, it gradu- 

 ally disolves. This is said to be owing to chemical 



