OF THE LEAVES, &C. 



Plants that are excluded from the presence of 

 the sun and light, and the free circulation of 

 air, give out carbonic acid gas : thus when plants 

 are crowded together and overshadow each 

 other, they are, by a waste of their carbon, 

 thrown off as carbonic acid gas, debilitated and 

 deprived of the needful stamina; which is often 

 followed by sterility, putrefaction, disease, and 

 death. 



An attention to these principles will enable 

 the husbandman, with great accuracy, to judge 

 of the difference between thick and thin sowing, 

 and to determine the proper medium ; and will 

 show the folly of removing or destroying the 

 leaves of plants designed to produce seed, fruit, 

 or roots, until these are perfected. 



ii 



