The potato; a practical treatise on the potato, its characteristics, planting, cultivation, harvesting, storing, marketing, insects, and diseases and their remedies, etc., etc

Preface

The literature issued on the subject of potatoes during the past three hundred years would form a large library, many works having been published in the United States, the United Kingdom, France, Germany, and other countries. It is safe to say that no plant has aroused a deeper interest than ' ' the noble tuber. ' ' Its very existence to-day is largely due to the efforts of enthusiasts. Several of the older writers were keen observers and acquainted intimately with the history and character of the potato, and modern authors include the names of men who are eminent in the scientific world. The vast amount of research and demonstration carried out by the experiment stations of this country during the past ten years, and the fact that every station has done something in this line, show the breadth of the subject and furnish material hitherto unobtainable. The excellent research work now being carried on in Europe, especially in France, Germany, etc., and more recently established in Ireland, indicates a demand for more information about this crop. We feel that the "science of agriculture" is a reality ; that, like every past generation, we are on the eve of great discoveries; that something of the laws governing plant nutrition and growth will shortly be revealed, that we may be able to prevent rather than cure the troubles which assail our plants. To be of

vii

Vlll PREFACE

any use, scientific research must be rigidly accurate in its observation and merciless to fallacy in logic. Once a principle is proven it is of no use unless applied, and the man to apply it is the farmer.

At the present time it behooves us to divest ourselves of prejudice, whether of tradition or custom, which might tend to warp our judgment and treat as debatable assumptions which long-established association have made shameful to doubt, but which, undisturbed, would make the discovery of truth impossible. To-day theories are no longer revered because our fathers believed in them. The search-light of allprying Science illuminates the whole field of agriculture, and has led men to doubt and call in question even truth itself , in order that they might expose those things which are not true. It is by this means alone, by this attitude of questioning all statements and theories, both the truth and the untruth alike, that we can form a just estimate of what is true. That which cannot stand the fire may rightly be esteemed dross.

In this book the endeavor has been to colledl many scattered fadls from many sources, and present these — along with experience derived by growing potatoes for several years, commercially and experimentally, in two continents — in the hope that these data will be of value to the reader.

Samuel Fraser.

Cornell University,

Ithaca, N. Y., 1905

Note.— With the exception of Figs. 26, 27, 28, 29, 30, 31, 43, and 44, which were kindly loaned by the makers of these implements, and those in which credit is given in the text, all illustrations have been prepared by the Author.

Chapter I Pages

History and Botany . 1-7

CHAPTER II Some Conditions Influencing Growth

and Development 8-16

Influence of Light on Yield, 8; Amount of Moisture, 8; Respiration, 9; Influence of Temperature on Respiration, 9; Influence of Temperature on Growth, 10; Potato Roots, 10; Influence of Depth of Planting on Roots, 15; Blossoming, Tuber Formation, and Hilling, 16.

CHAPTER III Soils 17-25

Best Soils, and Reasons why Certain Soils are Better than Others, 17; Influence of Soil on Different Varieties, 19; Subsoiling, 20; Preparation of the Soil, 21; Surface-fitting Tools, 23.

CHAPTER V Manuring and Fertilizing 30-50

Object, 30; Influence of Nitrogen, 31; Influence of Potash, 32; Sources of Potash, 33; Influence of Phosphoric Acid, 34; Influence of Calcium, 35; Barn Manure, 36; Function of Fertilizers, 39; Purchasing and Applying Fertilizers, 42; Value, 43; Unit Value, 44, Purchasing, 44; Valuing Barn Manure, 44; Mixing Fertilizers, 46; Applying Fertilizers, 48; Water Requirement, 48.

X CONTENTS

Chapter VI Pages

Source of Seed, 51; Management of Seed Previous to Planting, 53; Sprouting Potatoes, 54; Sprouting Trays, 60; Whole vs. Cut Sets, 60; Time to Cut, 61; Size of Seed, 61; Amount of Seed per Acre, 63; Relative Value of Bud and Stem Ends and the Middle of the Tuber, 66; Viability, 66.

CHAPTER VII Varieties 70-90

Selecting a Variety, 70; Cooking Quality and Flavor, 70, 72; Yield, 70, 74; Ability to Resist Disease, 71, 76; Color of Skin and Tuber, 71, 76; Nature of the Skin, 71, 78; The Shape, 71, 78; Depth and Frequency of Eyes, 71, 79; Time of Maturity, 71, 79: The Haulm, 71, 80; The Leaf, 71, 81; The Vigor of the Variety, 71, 82; Second Growth, 71, 85; Trueness to Type, 72, 85; Testing Varieties, 86; The Relationship of Variety to Soil, 87; The Most Popular Varieties, 87.

CHAPTER VIII Planting 91-104

Distance Apart,. 91; Depth of Planting, 93; Influence of Depth of Planting on the Depth at Which Tubers Form, 94; Influence of Depth on Quality, 96; Date of Planting, 96; Influence of Late and Early Planting, 97; Methods of Planting, 97.

CHAPTER IX Management of the Growing Crop. . 1 05-110

Cultivation, 105; Systems of Culture, 106; Hills, 106; Drills, 106; Level Culture, 107; Method of Cultivation and Tools Used, 107; Mulching, no.

CONTENTS XI

Chapter X Pages

Obstructions to Growth and Development 111-127

Influence of Season and Climate, in; Weeds, 112; Diseases Due to Parasitic Fungi and Bacteria, 112; Late Blight or Rot, 112; Early Blight or Leaf Spot Disease, 118; Potato Rosette, 118; Scab, 119; Diseases in Storage, 121; Wet Rot, 121; Dry Rot, 122; Stem Rot or Bundle Blackening, 122; Bacterial Diseases, 122; Insects, 123; Flea-beetle, 123; Potato Bug, 124; Potato Worm, 125; Potato Stalk Weevil, 126; Grasshoppers, 126; June Bug, 126; Wireworms, 127; Striped Blister Beetle, 127; Arsenical Poisoning, 127.

CHAPTER XI Sprays and Spraying 128-142

Fungicides, 128; Bordeaux Mixture, 128; Mixing, 129; Testing Bordeaux Mixture, 130; Strength of Solution, 130; Bordeaux Dust or Dry Bordeaux Mixture, 130 ; Washing Soda and Copper Sulphate Mixture, 131; Benefits from Use of Bordeaux Mixture, 131; Time of Spraying, 134; Number of Sprayings, 134 ; Insecticides, 135 ; Paris Green, 136; Lead Compounds, 137; Arsenic and Lime,- 138; Cost of Spraying and Profits Derived, 139; Spraying Machines, 140.

CHAPTER XVI Breeding and Selection 171-177 Propagation and Breeding, 171; Selection, 175

Spray Calendar, 178; Seed Treatment, 179.

Index 181

ILLUSTRATIONS

FIG. PAGE

Spraying in a New York Potato Field . Frontispiece

2 Copy of Engraving of the Virginian Potato from

Gerard's "Herbal," 1636 2

3 Sectional View of Potato Flower 4

4 Tuber, Showing the Arrangement of the Eyes . . 6

5 Potato Plant, Showing Tubers (Viewed from Above) 12

6 Potato Plant, Showing Tubers and Roots (Side View) 13

7 A Useful Type of Spring-tooth Harrow 22

8 A Disk Harrow , . . . 23

9 A Double-action Cutaway Harrow 24

10 The Influence of Lime Upon Potatoes 36

11 Potato Tray for Storing and Sprouting Seed ... 53

12 Potato Planted Four Inches Deep, Showing its

Growth and Development of Tubers 55

13 Seed Potatoes Sprouted for Use in the Planter . . 56

14 Seed of Early Potatoes, Sprouted for Hand Planting 56

15 Seed Potatoes, Showing Weak, Long Sprouts ... 57

16 Diagram, Showing the Stand of Twenty Plats of

Carman No. 3 Potatoes 63

17 Diagram, Showing the Stand of Thirty-six Plats

of Early Trumbull Potatoes 68

18 Section of a Tuber of Poor Cooking Quality ... 72

19 Section of a Tuber of Good Cooking Quality ... 73

20 Three Varieties Differing in the Character of Net-

ting of the Skin 77

xiii xiv ILLUSTRATIONS

FIG. PAGE

21 Three Favorite Shapes of Potatoes 79

22 Potato Plant, Showing Upright Haulm 80

23 Potato Plant, Early Variety, Showing Dwarf Haulm 92

24 The Modern Method of Planting Potatoes .... 98

25 Planting by Hand 99

26 Sectional View of the Aspinwall Potato Planter. . 100

27 Aspinwall Potato Planter (Side View) 101

28 The Robbins Improved Planter 103

29 Platform of the Robbins Improved Planter . . . 104

30 Halleck Expansible Weeder 107

31 Five-tooth Cultivator, with Hiller Attachment . . 108

32 A Useful Two-horse Cultivator 109

33 One-horse Spring Tooth Cultivator no

34 Section of Potato Leaf, Showing the Parts and

Mycelium of Blight (Pkytophthora infestans) . . 114

35 Maturation of a Spore Sac and Germination of a

Spore of Rot (P. infestans) 115

36 Longitudinal Section of a Potato Stalk, Showing a

Germinating Spore of Rot (P. infestans) . . . . 116

37 The Germinating Tube of a Spore of Rot (P. infes-

tans) on a Leaf 117

38 Tubers with and without Scab 120

39 The Cucumber Flea-beetle (Crepidodera Epitrix cucu-

meris) 123

40 Leaflet of Potato, Showing Over a Hundred Holes

Made by Flea-beetles 123

41 Sprayed and Unsprayed Portions of a New York

Potato Field 133

42 A Suggestive English Spraying Machine .... 140

43 The Reuther Potato Digger . . 145

44 The Hoover Digger . 146

45 Potato Shovel 147

ILLUSTRATIONS XV

FIG. PAGE

46 Storing Potatoes in Pits 148

47 Showing the Distribution of Potato Production in

the United States in 1899 154

48 Showing the Distribution of the Area in the United

States in Potatoes in 1899 155

49 Grading and Barreling Potatoes for Market . . . 163

50 Potato Flower, with Calix and Corolla Removed,

Showing Anthers and Stigma . . . . . . . 173

51 Pistil of Potato Flower, Showing Parts 174

ABBREVIATIONS USED

U. S. D. A. — United States Department of Agriculture, in connection with reports or bulletins.

E. S. R., V:33 — Experiment Station Record, Volume V., page 33. Issued by the United States Department of Agriculture, Office of Experiment Stations.

Experiment Stations in the various States are designated by the common abbreviation for the State— as, "Wis.": Wisconsin. Where there are two stations in a State, the particular one is designated — as, New York (N. Y.) Cornell. The number of the bulletin follows. Some States issue their bulletins in volumes, thus: Tenn. Bui., Vol. XL, I., p. 116 — Tennessee Bulletin, Volume XL, No. I., page 116.

Pa. D. A. — Pennsylvania Department of Agriculture. State Departments of Agriculture are abbreviated in this manner.

Can. Exp. Farms Report, 1901, p. 117 — Canada Experimental Farms Report for 1901, page 117.

Ont. Agr. Col. and Farm Report, 1898, p. 158 — Ontario Agricultural College and Farm Report for 1898, page 158.

Hort. Trans., Vol. 1. — Horticultural Transactions of England, Vol. I.

Nat. His. of Car. — Natural History of Carolina. By Mark Catesby, F.R.S. Second Edition. London.

Proc. Assoc. Prom. Agr. Science — Proceedings of the Association for the Promotion of Agricultural Science (America).

xvi

Chapter I History And Botany

The potato {Solatium tuberosum*) , also called "white potato," "Irish potato," "English potato," or "round potato," is a native of the elevated valleys of Chili, Peru, and Mexico, one form of it being found as far north as Southern Colorado. The wild potatoes of Chili differ from the cultivated form, in that they produce seed-balls more freely.

Tobacco, tomato, egg-plant, capsicum, henbane, and belladonna all belong to the potato family, but of this large family of 1600 species but six bear tubers. Some of these latter — as, Darwin's potato {Solatium maglia) — were thought to have some value for crossing to produce a blight-proof new race, but so far success has not been attained in the latter respect. A variety of Solatium commersoni, another tuber-bearing plant, is now being boomed in Europe as a substitute for the common potato. The Arizona wild potato {Solatium jamesii) has been grown for many years in this country in various places, but its tubers are small and of little value. The Mexican or Central American potato {Solatium tuberosum var. boreale) is found native in Colorado.

fig. 2 — copy of engraving of the virginian potato in gerard's "herbal," printed in 1636

(Compare with photograph, Figs. 5, 6.) In England the name Virginian potato was used to designate its source.

The potato was probably introduced into that part of the United States now known as Virginia and North Carolina between the middle and close of the sixteenth century. It is claimed that in 1586 colonists returning from Virginia probably took the potato with

HISTORY AND BOTANY 3

them to England. The Spanish had previously carried it to Europe. Gerard's " Herbal," published in 1597, describes the potato, and the edition published in 1636 contains a woodcut representing the potato as it appeared about three hundred years ago (Fig. 2). The potato was more readily appreciated in this country than in Europe, and by the year 1722 it was a common article of food among the whites and Indians in Virginia and Carolina. 1 In Europe, with the exception of Ireland, potato growing made little progress until the middle of the eighteenth century.

The potato {Solanum tuberosum) is an annual, but is virtually perennial by means of its tubers. It has smooth, generally solid, more or less quadr angul ar, herbaceous sterns^ wj^jch often attain a hight of two to five feet. The stems are often furnished with membranous wings at their angles, and bear compound leaves formed of oval leaflets, between which are often found small, leafy growths. The flowers (Fig. 3) are borne in clusters, and have an entire, wheel-shaped, five-pointed corolla, varying in breadth from one to one and a half inches, and in color from pure white to purple. It is often claimed that many varieties do not flower, and of those which do a great number never bear fruit. This dearth of fruit is generally attributed to lack of pollen. In many varieties the stamens have degenerated, or do not open to let the pollen out. 2 Conditions seem to have an influence, as a variety may bear abundance of pollen and mature seed in one district, but not in another in the same year.

1 "Nat. His. of Carolina, ■" by Mark Catesby, F.R.S., 2d ed. 2 Halstead, Proc. Assoc. Prom. Agr. Science, 1888, p. 33, " Potato Flowers and Fruit."

The idea is prevalent that potatoes do not bloom so freely How as formerly. The facfts do not tend to confirm this. Mark Catesby, who was in this country in 1722 and 1726, wrote that "in Virginia and to the

FIG. 3 — SECTIONAL VIEW OF POTATO FLOWER {Diagrammatic) a— Ovary, b— Ovules, which finally become seeds, c — Calyx, niade up of green-colored leaves, d — Stigma. The pollen attaches itself at this place. e— Style, down which the pollen-tube passes to the ovary and ovules. p — Petals, white to purple in color. ^ — Stamens. The thick upper portion bears the pollen, and is known as the anther.

north thereof, they [potatoes] are annuals, and produce no flowers, while in Carolina and the Bahama Islands they produce flowers." Many varieties existed at that time, particularly in Virginia, and five kinds were common — the Common, Bermudas, Brimstone, Carrot,

HISTORY AND BOTANY 5

and Claret potatoes. The Bermuda potato was the only one that had a white flower, the flowers of all the other kinds being purple. This was the only Yariety that had a white skin, and was white fleshed. It was round in shape, more tender, and more delicate to raise than the others, and did not keep so well. 1

George Don, in 1831, enumerates seYeral English early Yarieties, and says that " none of the aboYe sorts, when true, produce blossoms." 2

At Wyoming Experiment Station, 3 in 1895, out °f 56 Yarieties grown 14 did not bloom, but in 1896 but 4 Yarieties failed to bloom out of 56, and onfy one variety, Blue Victor, failed to bloom in one of the two years. In other parts of the State all the Yarieties grown came into bloom. In New York, during 1904, the variety Blue Victor was profuse in its bloom, and bore abundance of seed-balls. Out of 300 Yarieties I have followed closely, having grown man)- for several years, I find that it is seldom that a variety will not bloom at some time in its life, and I am sure that many of the heaviest-yielding varieties bloom as freely as those of inferior merit. At Wyoming Experiment Station the ten heaviest yielding varieties all came into bloom both in 1895 and in 1896, in experiments conducted in various parts of the State.

The fruit, or seed-ball, is a globular or short oval berry, either green or green tinged with violet, brown, purplish, or yellowish in color, and from three-quarters to one and a half inches in diameter. It contains

1 "Nat. His. of Carolina," by Mark Catesby, F.R.S., 2d ed.

2 Don's "Gardener's Dictionary," 1831-S, Vol. IV., pp. 400-406.

small white kidney-shaped seeds embedded in the midst of a green and very acrid pulp (Fig. 3). These seeds are sown for the purpose of raising new varieties.

The main vertical underground stem varies in length with the depth of planting. This stem branches at intervals, and each branch enlarges at the end to form a tuber (Fig. 12). Usually -from two to four roots start

from the vertical underground stem at the base of each tuber-bearing branch, but roots may start where such branches are absent. This characteristic growth may be seen by growing a potato in a barrel half full of soil and manure, and watering it well; then, as the stem grows, place soil round it, thus increasing the length of the underground portion and the number of tuber-bearing branches. The tubers may be formed above ground, and whenever they are abundant in the axils of the leaves there are few or none below ground.

The tuber is an underground stem, and the eyes on it are equivalent to the leaf buds on a stem of a young peach or ailanthus. They are arranged more or less spirally in both cases (Fig. 4). From the eye a number of buds may start; hence, in the case of new and expensive varieties, the tubers may be split through the

FIG. 4 — KIDNEY-SHAPED

potato {Does Pride) Showing the alignment of the eyes, and that the terminal buds tend to start first. Note the short, thick, desirable shoots.

HISTORY AND BOTANY 7

eyes, if desired, and a shoot obtained from each half. As each shoot sets a root it may be broken off and transplanted, and another may start. By these means and great care a pound of seed tubers has been made to yield 2,558 pounds of potatoes in one season.

Historical Note. — The early history of the potato is obscure. The most authentic information I have secured is that Sir Robert Southwell, the President of the Royal Society of England, at the meeting held December 13, 1693, stated that the potato was brought into Ireland by his grandfather, who obtained tubers from Sir Walter Raleigh, after the return of his expedition from Virginia. This was in the year 1584. It is now believed that Sir Walter Raleigh fitted out this expedition, but did not lead it personally, and never was in Virginia.

Timbs' "Curiosities of History," page 233, places the date of its' introduction to the British Isles as 15S6.

Chapter II Some Conditions Influencing Growth And Development

It is common knowledge that a certain amount of heat and an adequate supply of air and moisture are essential for plant growth. All plants that have green leaves require light, in addition, to enable them to assimilate carbon dioxid from the air, dissociate it into its component parts, and elaborate the carbon into such complex substances as starch, sugar, and other carbohydrates.

Influence of Light on Yield. — E. Pagnoul 1 placed colored glass over different potato plants. Two plants under darkened glass elaborated 31 and 20 grams of starch respectively, while those under ordinary glass elaborated 170 and no grams; at the same time plants under normal conditions elaborated 223 and 361 grams. To the favorable influence of abundant light this writer attributes the large yield of potatoes in a season when the aggregate number of hours of sunshine is unusually large. At Wisconsin Experiment Station coldness and cloudiness were believed to be the causes of a poor yield. 2

The Amount of Moisture. — The amount of water the plant can obtain from the soil is closely cor-

SOME CONDITIONS INFLUENCING GROWTH 9

related with the mode of development. If the soil is very dry, and particularly if the tuber is cut, the seed tuber may be so weakened by loss of moisture that it cannot grow. If a tuber has access to but a small amount of water, there will be little or no root development, with little formation of leaf shoots, but tubers will be formed. Advantage is taken of this fact when small early potatoes are required, the tubers being placed in sand, in a cellar, when small tubers will form, but none or few leaves. Under certain conditions, with an abundance or excess of moisture, numerous leaf shoots and roots appear, but no tubers. An increase in the supply of moisture in the air has been found to favor the development of leaves on the shoots, where only scales were formed in an insufficient supply of moisture.

Respiration. — We may say that all plants breathe or take in oxygen and give off carbon dioxid. With potatoes this is a necessary function, and if checked, growth is injured. It is probable that light induces some conditions more favorable to increased respiration than darkness; hence, if the object is to store potatoes, it will be better to hold respiration at its lowest point and keep them in the dark. Respiration cannot go on without force or energy, and as this must be supplied, at least partly, from the tuber, it follows that active respiration will be attended by loss of weight, and this goes on very rapidly when the tuber sprouts.

If we wish to ' ' sprout ' ' tubers, the best conditions for doing so are still undetermined.

Influence of Temperature on Respiration. — All plants have a range of temperature at which respi-

IO THE POTATO

ration is normal. The minimum, optimum, and maximum temperatures have been ascertained for some plants. Young wheat plants will respire at as low a temperature as 28 F., or below freezing-point. The optimum temperature for wheat is about 104 F., while that of potato plants is about 113 F. The maximum for wheat is 113 F., while that for potatoes is about 131 ° F. In other words, the potato respires best at about 113 F., but should the temperature go above 131 ° F., the respiration will be somewhat less than before, and the vitality weakened ; hence, after a hot spell, when the temperature exceeds the maximum for respiration, it is noticeable that the potatoes fail and become more susceptible to the blight or other troubles, owing to their impaired constitution. By selection we might procure plants of greater vitality, capable of standing the higher temperatures, which would enable them to be better ' ' disease-resisters," Present-day potatoes thrive best in a cool climate.

Influence of Temperature on Growth. — The minimum temperature for germination of potato tubers is about 50 F.; hence, in the Northern States early planted tubers make little, or no growth unless planted shallow, and this is not desirable, except, perhaps, for the earliest varieties. It is better to germinate the tubers in the barn before planting, thus saving time (see Chapter VI., " Sprouting Potatoes ")•

Potato Roots. — Generally speaking, far more attention has been paid to the stems and leaves of plants than the roots, yet in order to cultivate the soil in a rational manner it is essential to know where the roots

SOME CONDITIONS INFLUENCING GROWTH II

are, their character, and requirements. Examination of the roots of Early Ohio potatoes, 1 made July 5, 1899, forty-three days after planting, about the time the crop received its third cultivation, showed that at this time there was little growth of fibrous roots — only the skeleton system supplied with numerous delicate root hairs. The seed tuber appeared to be sound and whole, but on closer examination it proved to be but a shell. Only a few eyes on the upper side of each tuber produced shoots; thus one hill produced three stalks from two eyes, and another had seven stalks springing from five eyes. The latter plant had more numerous but smaller roots than the former. Twenty-five small potatoes were set on the first plant, the largest of which were the size of a large pea. At this stage of development the main portion of the roots was in the surface eight inches, a few roots reached to the depth of eighteen inches, but the greatest root growth was in a horizontal direction. The roots from each hill had already met and interlaced, some having reached a length of two feet, the plants being three feet apart. At six inches from the hill some of the main lateral roots were but two and one-quarter inches from the surface of the ground, while midway between the rows their depth was barely three inches from the surface.

Further examination of Early Ohio potatoes seventytwo days after planting, when the tubers were nearly full size, showed that the main root growth was in the upper foot of soil ; several of the large horizontal roots were within three inches of the surface, and one was but one inch deep. Some of the vertical roots reached a depth of two and a half feet. The deep-growing roots are very tender and brittle and easily broken, differing in this respedl from corn roots. The horizontal roots send out vertical branches, which often descend to a depth of two feet or more.

Shallow tillage, such as hand-hoeing without hilling, retains all the roots. Moderately deep tillage with a five-tooth single horse-cultivator and slight hilling destroys practically all the surface roots, and undoubtedly interferes seriously with the plant's development ; while with deep tillage nearly all the long horizontal roots are destroyed, and with them all their numerous vertical branch-roots with their intricate system of fibres and root hairs, by which the potato receives its food. In very heavy soils it may be wise to plant potatoes shallow and then hill them, but in most soils it is better policy to plow deep, plant fairly deep, and give shallow flat cultivation. With deep tillage the roots nearest the surface were at a depth of seven inches, while in the case of those receiving shallow tillage the bulk of the horizontal roots were in the surface seven inches. The hilling covers the potatoes and prevents them from sunburning, and this seems to be all the benefit received. The loss of roots is very hurtful, and takes place at a time when the plant can least afford to suffer injury. Experiments condudled at Vermont Experiment Station 1 show that during the last weeks of growth the weekly increase in weight of tubers is at its maximum, and that checks when the tubers are approaching maturity depress the yield cor* respondingly.

SOME CONDITIONS INFLUENCING GROWTH 1 5

A sample of Early Ohio potatoes taken ninety days after planting, when the vines were beginning to die and the tubers were nearly ripe, showed that the roots penetrated to a depth of over two and a half feet. 1 The branches from the main lateral roots had reached about as deep as those immediately under the hill, and the soil was filled with roots to a depth of about two and a half feet. The system of rooting is similar to that of corn, but the plant is not so good a forager, and the roots do not fill the soil so completely; hence, plants can be placed closer together.

Late varieties have a similar root system, but root more freely, more deeply (a depth of three and a half feet being common if the soil conditions will permit), and occupy the ground more completely; hence, require more room than early varieties.

At Cornell University, during 1904, many potatoes had horizontal roots in the surface inch of soil. All of these would be destroyed by moderately deep tillage.

Influence of Depth of Planting on Roots. — Generally speaking, the new potatoes and the roots start out above the seed, although if an under eye of the potato produces the shoot the roots and tubers may develop at the side of the seed. Depth of planting has some influence on the depth at which the tubers will form, and may have some on the roots. The question deserves investigation. Many plants prefer to send out their roots at a uniform depth below the surface : thus, at Cornell University, wheat, whether planted six inches deep or one inch deep, will send out its permanent roots about one and a half inches below the surface.

Blossoming, Tuber Formation, and Hilling. —

Potatoes are hilled about the time they come into bloom, and this is the time that tuber formation is beginning. The ancestral type of potato developed seed about this time and died ; the tendency acquired by cultivation is to throw all the reserve material into tuber production. These reproductive processes cause a severe drain upon the plant's energies, and the fortnight immediately following the blossoming period is therefore a peculiarly critical time for the plant, during which time its life hangs in the balance. At this time it is subjedl to extreme heat, and may be injured; also insedts, fungi, etc., may attack it, and, to add to its troubles, cutting off a lot of its roots, either just before or about this time, is no doubt the common cause of a decline from which the plant never recovers. Even tuber formation, without the influence of other agencies, may cause a plant to die. The importance of studying the condition of the plant at this time will be appreciated when it is remembered that the entire crop of salable tubers is formed after this critical period is past, and full success with the crop depends upon retaining the plant healthy for from one to three months after the blossoming period. During August, in one case, 1 the crop of potatoes increased at the rate of over 50 bushels, or over 3,000 pounds, weekly per acre. The importance of avoiding checking growth preparatory to or during such a time is evident.