52 VERMONT AGRICULTURAL REPORT. 



as is now known, every one of these elements is essential to plant 

 growth. Four of them are derived from the air and ten from the soil; 

 eight of them are non-metallic and six of them are metals. The air- 

 derived elements are carbon, hydrogen, oxygen and nitrogen. These 

 are all non-metallic elements. The ten soil-derived elements are 

 phosphorus, silicon, chlorin and sulphur, which are non-metals; potas- 

 sium, sodium, calcium, magnesium, iron and aluminum, which are 

 metals. 



Over 95 per cent, of the entire structure of the average plant is air- 

 derived. There is no plant but what contains while alive very much 

 the largest proportion of its weight of water. Some kinds — lettuce, for 

 instance — carry as high as 96 per cent, of this ingredient. A large share 

 of the material other than water, moreover, is composed of car- 

 bonaceous matter, which is readily burned if the dry plant is set on 

 fire. Such materials as are directly derived from its soil are repre- 

 sented by the ashes. Although these constitute but a small proportion 

 of the total weight of the plant they are absolutely essential to its 

 growth. They cannot be held to be of little use because of the small 

 proportions used. The tongue, we are told, is an unruly member, and 

 it is but a small part of the human frame; but how would some of us, 

 particularly our sisters, get along without it? 



Plants possess two sets of mouths, so to speak. Some of their food 

 enters by way of the roots and some by way of the leaves. The latter 

 take carbon from air in the shape of a gas known as carbonic acid. It 

 is the same gas which bubbles in the soda water at the druggist's. From 

 this gas, together with the water absorbed by the roots, the bulk of the 

 food matter of plants is built. 



Had we time and space it were of interest, perhaps, to retail the story 

 of all of these fourteen elements. I could tell you of the wonders of 

 carbon, found pure in the diamond that sparkles in the crown of 

 royalty, or as the graphite of the lead pencil in the beggar's hands; of 

 the great accumulation of more or less pure carbon, as coal, and of the 

 wonderful way in which this coal is formed. I might tell you, more- 

 over, of silicon, which forms with oxygen the backbone or skeleton 

 of the world; of aluminum, that wonderful, light, non-tarnishing metal 

 which bids fair to revolutionize some of our industries. It does not seem 

 necessary to go into these details, however, for the reason that, while 

 these elements are of interest, ten of the fourteen exist in every soil in 

 such large quantities that plants will get enough without any attention 

 by man, no matter how many unending cycles of centuries elapse. 

 There are four of these elements, however, which do become more or 

 less readily exhausted from the soil and which, on this account, ought 

 to be well understood by everyone who has to do with agriculture. 

 Nitrogen, phosphoric acid, potash and lime enter largely into plant 

 growth, are apt to become more or less lacking in available forms in 

 soils, are the main ingredients in commercial fertilizers and are justly 

 called the deficient constituents of plant food. Their importance justi- 

 fies a special consideration of their nature and functions. 



