48 MY GARDEN. 



pears and perhaps more of apples, and there are innumerable varieties 

 of all the kinds of plants which the gardener cultivates in his flower- 

 garden. Nevertheless, we cannot change one plant into another, 

 though in practice it is sometimes extremely difficult to tell whether 

 a plant is a variety or a species. Good botanists differ widely on 

 this point in particular instances, some having a tendency to multiply 

 species, others to restrict them. Every seedling plant has an indi- 

 viduality of its own, as every human being presents some points of 

 difference, and the gardener selects those which best suit his particular 

 purpose. If one plant cannot be changed, and never has been changed, 

 into another, then it follows that each species has at some time in 

 the world's history been specifically created. I myself believe, and 

 most naturalists believe, that each species has been specifically created; 

 but it is as easy to conceive that one organic structure should have 

 been in the beginning created, which had the power under certain 

 changed external circumstances of being developed into the tens of 

 thousands of plants which live over the whole surface of the globe. 



Every plant is composed of carbon, hydrogen, and oxygen in 

 combination, water as water, and certain mineral matters which are 

 interspersed throughout the entire structure of the plant. The carbon 

 is obtained from the carbonic acid which exists invariably in the 

 atmosphere ; the compounds of nitrogen are derived from aqueous 

 solutions of ammonia or nitrates ; and the earthy salts are also ab- 

 sorbed from solutions of matters contained in the ground. 



The plant, to assimilate these matters to itself, must be acted 

 upon by the physical forces of heat and light, in an atmosphere 

 having a proper quantity of water. No gardener can succeed without 

 attending to all these points, as every species requires its own par- 

 ticular treatment. 



All plants reduce their carbon compounds, as the woody fibre, 

 starch, gum, and sugar, by means of their leaves, from the air, and 

 derive the nitrogenized principles, as their albumen, together with the 

 water and earthy salts, by means of their roots, from the ground. The 

 leaves, to perform properly their functions, require moisture in the 



