CULTURAL METHODS.

There still remains much to be determined regarding the best methods of growing Sudan grass. Several satisfactory ones have already been developed, the most promising being that of planting in closely cultivated rows in which the seed is sown thickly. (See Pl. LXVIII, fig. 1.) While broadcasting also gives good results, it does not seem to produce the yields that are obtained from cultivated rows, even under conditions of ample rainfall. An 18-inch row can be easily cultivated once or twice while the grass is young, and after it has attained a height of 2 feet or more additional cultivation does not appear to be necessary, either to keep down weeds or to promote further growth. For the production of seed, which is an important consideration at this time, the cultivated row is unquestionably to be preferred to broadcasting. It not only greatly increases the yield, but also facilitates harvesting. The yield of hay and seed from Sudan grass can as yet be only roughly approximated. Suffice it to say that in a vast majority of the cases reported the yield of hay has been unusually high and that of seed entirely satisfactory.

The reasons for predicting widespread popularity for this grass are based on its wonderful adaptability to various conditions, its ability to produce under these conditions profitable yields of excellent forage, and the ease with which it can be grown. With the numerous advantages which Sudan grass possesses, it promises to compete in a measure with Johnson grass in parts of the South, and generally with the sweet sorghums and the millets.

SUDAN GRASS SEED.

That there may be no misunderstanding regarding the resemblance of Sudan grass to Johnson grass, it must be distinctly understood that while the former is much the same as the latter in appearance, Sudan grass under no conditions produces rootstocks, and is at once eradicated by plowing. (See Pl. LXIX.) The question may arise as to whether, on account of the close similarity of the seed, Johnson grass may not inadvertently or otherwise be introduced by means of Sudan grass. This is entirely possible, but it can be obviated by sowing seed that is produced only in the North, where Johnson grass is not grown. At this stage, when the seed of Sudan grass is scarcely a commercial commodity, extreme caution should be used, as unscrupulous dealers will be inclined to adulterate it with seed of Johnson grass. Such a practice, however, will unquestionably fall into disuse in a comparatively short time, as the seed of Johnson grass will undoubtedly soon be the more expensive of the two. Seeds of these grasses may be quite readily distinguished after a little experience, those of Sudan grass being plumper than

those of Johnson grass and breaking from the seed head or panicle with a small portion of the rachis or branch. The seed of Johnson grass breaks off smoothly with a well-defined scar, and in this respect Tunis grass is quite similar to it. (See Pl. LXVIII, fig. 2.)

HYBRIDIZING WITH CULTIVATED SORGHUMS.

Owing to the close relationship between Sudan grass and the sweet sorghums, natural hybrids between them are abundantly produced where they are grown in close proximity to each other. A number of these hybrids have been isolated by the department and are quite promising. (See Pl. LXX.) For the present, however, it is advisable to keep the two crops separate and to rogue out any variations that may appear in the Sudan-grass fields in order that the true type may be maintained.

Sudan grass already needs no exploitation, and it hardly seems likely that anything will develop to detract from its popularity or to lessen its usefulness. Numerous representatives of its group (the sorghums) are now, and have been for a long time, important forage crops in this country. Taking this into consideration, together with the wonderful showing Sudan grass has made, the predicting of a bright future for it seems entirely justified.

RAISINS, FIGS, AND OTHER DRIED FRUITS AND THEIR

USE.

By C. F. LANGWORTHY,

Chief of Nutrition Investigations, Office of Experiment Stations.

INTRODUCTION.

66

In discussing the food value of fresh fruits the common varieties. are frequently divided into two groups-those whose water content is so high that their value lies mainly in the pleasant flavor and healthful variety that they give to the diet and those which contain sufficient quantities of nutritive ingredients to add noticeably to the food value of the total diet. Roughly speaking, those whose water content is 80 per cent or over are classed as flavor fruits." This class includes the majority of our common fruits, e. g., apples, pears, peaches, plums, oranges, most berries, etc. The banana is perhaps the most often called a "food fruit." that is, one whose water content is less than 80 per cent, but grapes, figs, and olives are other wellknown members of the group. When dried fruits are under consideration this distinction between flavor and food fruits disappears. The amount of water in dried fruits depends upon the degree of desiccation rather than upon the original composition of the fruit, and the latter is therefore no guide to the food value of the dried product.

Of course the flavor of dried fruits is almost never the same as that of fresh fruits; for eating in the simple state, and for some, though not all, cooking purposes, fresh fruits would usually be preferred" were they equally convenient. As everyone knows, fresh fruit will not keep indefinitely, even with the most careful storage, and it is, moreover, so bulky that shipping it from place to place and providing storage room is decidedly expensive. Drying has the double advantage of protecting against decay and rendering the fruit more compact, while at the same time a product results which is palatable and convenient. A pound of fresh fruit will yield an average of about 6 ounces dried. The food value of a pound of dried fruit is, of course, greater than that of the same weight of fresh, since it has been concentrated by evaporating the water originally present.

The main change which takes place during drying is a loss of water, but other changes also occur, their nature varying greatly with different kinds of fruit and with different methods of drying, particularly with the degree of heat employed. Very often the right

degree of heat produces changes not unlike those which occur during natural ripening on the plant. In general the carbohydrates which make up the largest part of the solid matter of the fruit undergo the most extensive changes. In some cases the crude fiber, which forms the basis of the plant structure, is reduced in amount or softened. Much of the starch is changed to some form of sugar, and the less soluble sugar may be reduced to more soluble forms. The change in flavor is due partly to the proportionate increase of sugar from loss of water and absolute increase from the chemical changes just referred to; partly to the fact that some of the volatile oils and other ethereal bodies, which give the distinctive flavors to fresh fruits, pass off or are modified during the drying process; and partly to a lessening or masking of fruit acids and to certain chemical changes in the tannin by which its characteristic "puckery" flavor is lessened and by changes in other substances of the fruit.

Dried fruits probably first appeared in warm countries, but they have long been known among the peoples of northern latitudes. Certainly in America the practice of drying fruits has been common ever since the first settlements by Europeans. Dried apples and berries played a prominent part in winter menus of colonial times, as they had in the winter supplies of the Indians, though the methods of drying were crude and the dried fruit often poor and irregular in quality. Of recent years the rapid improvement in machinery and methods of drying have given a great impetus to the dried-fruit industry, and artificial drying produces so much better results that it has very largely superseded the old-fashioned methods for apples, apricots, peaches, and most of the fruits grown in the northern parts of this continent and Europe. The cost of fuel and equipment is more than offset by the economy of time and labor, to say nothing of the greater cleanliness and uniformity of the fruit so prepared. Artificial drying is usually practiced on so large a scale that it is economical to have special rooms or apparatus for each part of the process, and this eliminates much of the handling and exposure to dust and dirt and insects, which were likely to make fruits dried by the old-fashioned methods so unattractive or even unhealthful.

Questions of fruit production and preservation have been studied, with very important results, by the Department of Agriculture and the agricultural experiment stations. To this work and the efforts of the American fruit growers may be attributed the great development of the dried-fruit industry in the United States in recent years.

THE PREPARATION OF DRIED AND EVAPORATED FRUITS.

Drying, evaporating, and desiccating are all terms used to describe the making of the fruit products under consideration. There are no

very definite distinctions which can be drawn between fruits prepared by such processes, though perhaps "dried fruit" is the broadest term. Removing the water depends chiefly on heat and the pressure and water content of the air surrounding the fruit and the rapidity with which the air circulates. The lower the air pressure, the drier and the warmer the air, and the more rapidly it moves, the more easily the fruit will give up its watery juice. If the process of drying is too rapid or too slow, or if the degree of heat is too great or too little, the resulting product will be below standard. The different methods and devices for preparing dried fruits have resulted from a recognition of such facts and an attempt to apply them accurately. The liking for one or the other is a matter of personal preference and habit, but the rapid drying achieved by modern methods gives a superior product of different flavor as well as of different color and texture from the old-fashioned home-dried fruit.

From the point of view of those who finally eat the fruit, the main thing is to have it dried in such a way that it shall retain as much of the natural flavor and food ingredients as possible, together with soft texture, attractive appearance, good keeping qualities, and freedom from insects or dirt or harmful substances of any kind.

For some kinds of fruit, especially for raisins and figs, artificial drying does not work as well as sun drying. The great difficulty with natural drying in the open air, aside from the uncertainty of the weather, is, of course, the exposure to dust and insects. Everyone knows that dust may be the bearer of all sorts of microorganisms, causing disease, and of other tiny organisms which cause decay in the fruit. Insects, attracted by the sweet fruit, introduce future worms by laying their eggs in it. It is possible to guard against these dangers by choosing clean and protected drying places, by preventing careless and unnecessary exposure, by washing or sterilizing, and by careful packing and marketing. The large establishments in the fruit-growing sections of the United States are setting high standards of cleanliness and are demonstrating that it is profitable to produce really sanitary goods. Unfortunately such conditions do not prevail in some of the countries around the eastern end of the Mediterranean, from which comes such a large part of the world's dried figs and dates.

Preparing dried fruits for the market is a more complicated process than is commonly realized. The modes of procedure naturally vary in different localities and for different kinds of fruit, but they can all be shown to depend on scientific principles, even though those who apply them may not have taken this into account. The housekeeper who dried her own apples may not have understood that the tannin present in the flesh of fruit is acted upon by oxidases when exposed to the air, or that salt inhibits such action, but she knew that the