In Class I. Phosphates and Potash predominate.  This class consists of the less succulent plants, and includes the following:  The Pea:  containing, in 100 parts of the ashes, phosphates, thirty-six; potash, forty.  Bean:  phosphates, thirty; potash, forty-four.  Potato (tubers only):  phosphates, nineteen; potash, fifty-nine; soda, two; lime, two; sulphuric acid, six.  Parsnip:  phosphates, eighteen; potash, thirty-six; lime, eleven; salt, five.  Carrot:  phosphates, twelve; potash, thirty-six; soda, thirteen; sulphuric acid, six.  Jerusalem Artichoke:  phosphates, sixteen; potash, sixty-five.

In Class II.  Sulphur, Lime and Soda Salts are predominant.  This class consists of the more succulent plants, and includes the following:  Cabbage:  containing, in 100 parts of the ashes, phosphates, sixteen; potash, forty-eight; soda, four; lime, fifteen; sulphuric acid, eight.  Turnip:  phosphates, thirteen; potash, thirty-nine; soda, five; lime, ten; sulphuric acid, fourteen.  Beet:  phosphates, fourteen; potash, forty-nine; soda, nineteen; lime, six; sulphuric acid, five.

As a matter of course, Lentils and other kinds of pulse agree more or less with Peas and Beans in the predominance of phosphates and potash.  So, again, all the Brassicas, whether Kales, Cauliflower, or whatever else, agree nearly with the Cabbage in the prominent presence of lime and sulphur; ingredients which fully account for the offensive odour of these vegetables when in a state of decay.  Fruits as a rule are highly charged with alkalies, and are rarely deficient in phosphates; moreover, stone-fruits require lime, for they have to make bone as well as flesh when they produce a crop.  As regards the alkalies, plants appear capable of substituting soda for potash under some circumstances, but it would not be prudent for the cultivator to assume that the cheaper alkali might take the place of the more costly one as a mineral agent, for Nature is stern and constant in her ways, and it can hardly be supposed that a plant in which potash normally predominates can attain to perfection in a soil deficient in potash, however well supplied it may be with soda.  The cheaper alkali in combination as salt (chloride of sodium) may, however, be usually employed in aid of quick-growing green crops; and more or less with tap-roots and Brassicas.  Salt, too, is very useful in a dry season by reason of its power of attracting and retaining moisture.  As regards Potatoes, it is worthy of observation that they contain but a trace of silica, and yet they generally thrive on sand, and in many instances crops grown on sand are free from disease and of high quality, although the weight may not be great.  The mechanical texture of the soil has much to do with this; and when that is aided by a supply of potash and phosphates, whether from farmyard manure or artificials, sandy soils become highly productive of Potatoes of the very finest quality.  On the other hand, Potatoes also grow well on limestone and chalk, and yet there is but little lime in them.  Here, again, mechanical texture explains the case in part, and it is further explained by the sufficiency of potash and phosphates, as also of magnesia, which enters in a special manner into the mineral constitution of this root.