Plant Physiology, Theoretic and Applied. 339 



dry and porous. Even where the soil is level and texture everything one could 

 desire, even here great are the sins of irrigation in many instances. Often 

 men seem to have the idea that unless the irrigation water is standing for days 

 and even weeks in their orchards, the trees are not drinking enough. In a 

 sentence let me urge upon you, abandon excessive irrigation with streams of 

 water, and do most of your irrigation with the plow and harrow ; urge upwards 

 the flow of water by capillary action from below, keeping it .iust beneath the 

 surface by a mulch of finely pulverized earth. Of course these remarks can not 

 apply to those irrigated orchards which liave been "put down" in clover and 

 grass. Such orchards need more water, and can only receive it in one way, but 

 even such orchards should not be allowed to remain many years in this condition, 

 but should after a reasonable lapse of time be plowed up, the clover and grass 

 plowed under, and bare cultivation resorted to for a few years, when another 

 crop can be put in. This gives the trees a chance to collect more oxygen about 

 their roots, and allows them at times to thirst for water — as good a thing for 

 trees occassionally as for man. 



But, besides water, what are these numerous root-hairs taking from the 

 soil and conveying to the leaves? The three most evident elements in a fruit 

 tree are carbon, which is taken mainly from the air through the breathing 

 pores or "stomata," and oxygen with hydrogen in the form of water. But 

 though the greater part of roots, stem, and leaves are composed of these three 

 elements, there are others as essential. Nitrogen, so abundant in the air, but 

 nn.ivailable to the plant, must be given it through the earth. Without nitrogen 

 there could De no life, for all life depends upon the working of protoplasm, 

 and protoplasm is dependent absolutely upon nitrogen. So we must have an 

 abundance of this element in the soil, and if it is not present in your land 

 produce it by heavy manuring, or better still by growing leguminous crops 

 amongst your trees, and occasionally turning them under with the plow. There 

 is probably no such simple and at the same time profitable way of giving 

 nitrogen to the soil as this, for the leguminous crops, as nearly every one knows 

 at this time, are the harborers and workships for numerous nitrifying microbes 

 or bacteria by means of the nodules on their roots. Sulphur and phosphorus 

 there must also be in the soil to some extent, as they both seem intimately 

 connected with the working of the protoplasm. Plants grown in a soil poorly 

 supplied with phosphorus have generally a red color, while land having but 

 little iron gives a yellow color to the plants. In fact no chlorophyll, or green 

 coloring matter, so essential to all independent plants, can be formed at all 

 without the presence of iron. Potassium should be found in the soil, also, in 

 limited quantities, as it seems intimately connected with the production of the 

 carbohydrates, such as starch, sugar, and cell material, or cellulose. While 

 the plant cannot form chlorophyll without iron, it will not make the chlorophyll 

 do its work and form starch, if deprived of potassium. In a few words, calcium, 

 in some of the combinations of lime, and magnesium, both in small amounts, 

 are absolutely required in the plant's economy ; sodium and silica, or sand, 

 though formed in most plants do not seem needed in all. The latter is found 

 in greatest abundance in oaks, scouring rushes, and the frustules or cases of 

 diatons, which are made up almost entirely of pure glass. 



An eminent European authority well expresses what a good condition of 

 soil should be when he says, "An ideal condition of soil is one in which it 

 resembles a sponge, and in which it will retain the greatest amount of nutritive 

 substances and water, without losing its capacity of absorbing air." 



TRANSPLANTING AND HOOT PRUNING. 



Before concluding our study of the root system, it becomes very necessary 

 that we consider when and how we should transplant. Besides speaking of this 

 in its proper season, we should also consider the occasional, but none the less 

 necessary, transplanting out of season. 



Whether spring or fall be the better season for putting out an orchard, I 



