No. 1. iDEPARTMENT OF AGRICULTURE. , 23S 



SO. Chemists in the Experiment Stations have for many years 

 been dividing up the phosphatic fertilizers which have beeu treated 

 with sulphuric acid into the soluble, or water-soluble, the reverted, 

 or citric acid-soluble, and the insoluble. Many of the Stations in 

 their estimates of the value of the fertilizers carrying phosphorus 

 have placed no value at all on the insoluble phosphoric acid in them, 

 or at best a very low value. But we are fast learning that some- 

 things happen in the great laboratory of Nature which our little 

 laboratories told us nothing about, and it has now been found that 

 in a soil abounding in humus we may place the insoluble pulverized 

 phosphate rock, and it will rapidly become soluble and available to 

 plants. But equally important is the fact that humus is more re- 

 tentive of moisture than anything else that goes to make i5p a soil, 

 so that a soil abounding in humus will stand more drought than 

 soil of any other character. The vast importance of this fact will 

 be realized when we reflect that plants cannot take any food from 

 the soil until it is in perfect solution in the soil Avater. Hence the 

 retention of moisture for this purpose is of the greatest import- 

 ance. 



But if you will pardon me, I would like to digress a while from 

 the direct subject, and endeavor to explain to some extent how 

 plants which make up our crops grow and get their food from 

 soil and air. There is more ignorance in regard to the anatomy 

 and functions of plant life, even among men considered educated, 

 than about anything else apertaiuiag to agriculture. But in order 

 fully to understand how we are to improve our soils and make them 

 more productive in crops, we should fully understand how plants 

 live and grow in order that we may know how and with what to 

 feed them. 



There has been a great deal said of late years about a certain 

 order of plants, the legumes, which, through the agency of certain 

 minute organisms of the low order of plant life, known as bacteria, 

 are enabled to get and combine in an available form the free nitrogen 

 that exists so abundantly as a gas in the air. Of these will speak 

 later. But is is not so generally realized that all plants get far more 

 of their structure from the air than they get from the soil. More 

 than ninety per cent, of the organic structure of every plant comes 

 from the air, and less than ten per cent, from the soil. Growth 

 in plants is made by the increase in number and size of little box- 

 like structures called cells. Cut across the stem of any woody plant 

 and examine the cut end with a lens of even moderate magnifying 

 power, and you w^ll see that the rings of growth are really circles 

 of these cells, larger and thinner walled in the spring, and gradually 

 becoming smaller and thicker walled as the close of the season of 

 growth is reached, so that to the naked eye they merely look like 

 rings. These little cells are filled at first with a formless substance 

 similar to the white of an egg, Avhich biologists call protoplasm. 

 This is the only material in the plant that possesses life, and this 

 formless living matter carries with it and constructs the material of 

 which the cell walls are made. In short, the growth of a tree is made 

 of constantly increasing circles of cells somewhat after the manner 

 of building a wall with bricks, only that in this case the brick- 

 maker and the mason live inside the bricks and form from their own 

 substance the walls that confine them. In the first thin growing 

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