152 



THE GAEDENER'S ASSISTANT. 



The amount of dry substance accumulated by 

 the plants from the soil during their early 

 growth as cuttings may be stated as follows : — 



Dry substance in leaves, 52 per cent. 

 ,, ,, stems, 45 ,, 



,, „ roots, 77 „ 



One-year-old plants of Azalea contain in their 

 different organs for each one hundred of dry 

 substance accumulated, the following amounts 

 of nitrogen and mineral matter (ash) : — 



Parts of the Plant. 



Nitrogen. Mixed Matter (Ash). 



Flowers, 

 Leaves, 

 Stems, 

 Roots, 



per cent. 

 2-62 

 1-86 

 1-12 

 0-96 



per cent. 



(?) 



3-80 

 4-20 

 5-30 



The following analysis shows the composition 

 of the mineral matter (ashes) of the different 

 organs of the Azalea plant : — 



Selected Constituents. 



Leaves. 



Stems. 



Roots. 





per cent. 



per cent. 



per cent. 



Potash, 



8-88 



1420 



8-29 



Phosphoric acid, ... 



6-88 



5-76 



3-20 



Lime, 



18-90 



21-72 



213 



Iron oxide, ... 



012 



0-12 



o-io 



Silica, 



46-00 



27-20 



78-00 



These results teach us that the quantity of 

 nitrogen contained in the leaf-mould used for 

 these experiments was much beyond the require- 

 ments of the Azalea. But as this nitrogen 

 exists in the mould in combination with other 

 organic matters it does not become soluble, and 

 in a condition to be absorbed by the plant, 

 except by very slow degrees. Consequently 

 the actual amount of nitrogenous plant-food 

 provided can only be reckoned by the nitric 

 nitrogen which is transformed and made as- 

 similable by the process of nitrification, and 

 which takes place in the soil during growth. 



From the average of many experiments it 

 was found that in the course of one year a 

 superficial yard of the mould used would yield 

 by nitrification the following amounts of nitric 

 nitrogen : — 



Peat-mould, 

 Leaf-mould, 



Total in 1 yard, 



Weight in h yard. Nitrogen in J yard. 

 61-5 lbs. 10-88 grammes. 



6S-5 „ 37-01 



130-0 



47 -89 



Thus, during the first year of growth of the 

 Azalea plants there would be placed at their 

 disposal in each yard of mould, equal 130 lbs., 

 47*89 grammes of soluble nitrogenous food, 

 while the analysis of the different organs of the 

 plants showed that they had absorbed only 



14-77 grammes. It is tolerably certain that in 

 leaf-moulds, where organic matter (humus) and 

 lime exist in any quantity, the nitrification that 

 goes on is most intense, and must provide abun- 

 dance of the richest plant-food. 



Turning now to a consideration of the mineral 

 ingredients placed at the disposal of the plants 

 by Ghent leaf-mould, and the leaf-moulds from 

 Versailles, during the period of one year 

 find the following results : — 



we 



Selected Constituents. 



Ghent 

 Leaf-mould. 



Maurepas equal 

 parts Leaf and 

 Peat Moulds. 



Lime, 



Phosphoric acid, 

 Potash, 



grammes. 



107-07 



17-13 



24-78 



grammes. 

 56-54 

 11-03 

 36-44 



These figures show that the Ghent mould 

 produces in an equal period of time 35 per cent 

 more assimilable phosphoric acid, and about 48 

 per cent more of lime. Therefore, by adding a 

 phosphatic manure to the French leaf-moulds 

 to supply the deficiency of phosphoric acid, it is 

 possible to obtain a mould of equal value with 

 the Ghent mould. 



If a gardener has to do with a soil which is 

 naturally rich, like the Ghent leaf-mould, a soil 

 which may contain in its upper layers, say 1000 

 lbs. of phosphoric acid per acre, from which the 

 plants may draw without stint the amount they 

 require, then the demands on the solubility of 

 the phosphate are small. But if, on the other 

 hand, the soil is deficient in phosphoric acid, or 

 contains this constituent in comparatively small 

 quantities, as the Maurepas moulds, then the 

 demands on the solubility of the phosphate are 

 naturally much greater. The mould rich in 

 phosphoric acid would need only to supply the 

 plants with a phosphate manure of which say 

 5 per cent was soluble; but the mould poor in 

 phosphoric acid must be provided with a phos- 

 phate manure of which not less than 10 per 

 cent is soluble in order to obtain equal results. 

 Hence, to raise the moulds of Versailles to a 

 point of equal productiveness with the Ghent 

 mould, even in the first year of growth of the 

 Azalea, an application of bone-meal, phosphate 

 powder (basic slag), or mineral superphosphate 

 must be applied. 



Second Year of Growth. — In the month of 

 April of the second year, the greater number 

 of the' young plants were covered with flowers; 

 these blooms were found to contain about 6 per 

 cent of dry substance and 2-8 per cent of nitro- 

 gen. It was surprising to find that the Azalea 

 flowers contained 44 -3 per cent of sugar in their 



