They are objectionable because of being difficult to harvest, and because they hold considerable soil and are likely to have coarse and stringy flesh.
The dimples (D), usually two in number, are depres sions on opposite sides of the root. They should be vertical and not too deep.
The lateral roots should be fine, fibrous and abundant, and should arise only from the dimples, otherwise they increase the cost of harvesting and carry considerable soil, which is objectionable. The fibrous roots springing from the taproot break off when the root is harvested. They are extensive and frequently fill the soil to a depth of four or five feet. The flesh is seldom of a uniform color.
A transverse section w ill show rings of firm tissue alter nating with rings of softer tissue. Six or seven or more rings are often formed in as many months of growth. The sap of the soft tissue is often colored, being crimson or golden, or other color, even white.
In the manufacture of sugar from sugar-beets considerable loss was experienced in removing the coloring matter from the sap, and this led to the use of white mangels for sugar production.
History of mangels.
The mangel is regarded as a direct descendant of the chard, which was used by the Greeks 300 B.C. as a vegetable. The roots of the chard were used medicinally and as a vegetable during the first and second centuries A. D. The use of the root for cattle-feeding is recorded as early as the sixteenth century, and beets were introduced into this coun try by the early colonists. As late as 1783 the only kinds of mangel seed catalogued for sale in England were the red beet and the common long red, and in 1806 the red beet was the only kind listed in America ; in 1828 four varieties were mentioned and today there are probably not over a score in common use. Since 1805, when the manufacture of beet-sugar began, certain man gels have been developed and have produced our present-day sugar-beets.
Geographical distribution.
The wild plant (Beta cal garis, Linn.) may be found in digenous along the Mediter ranean and in other parts of Europe. It was originally cul tivated for its leaves under the name chard, and this plant is sparingly grown in American gardens. It was later grown for its roots, and about the middle of the sixteenth cen tury we have reports that in Germany and Italy and other parts of Europe the root was grown as stock-feed. The
practice of growing it as cat tle-feed was later introduced into the United Kingdom, where the industry was rap idly developed and where some of the best varieties are now found. The mangel is spar ingly grown in parts of the United States, but to a larger extent in Canada.
Composition. Figs. 776, 777.
The average percentage com position for mangels, sugar-beets and garden beets usually given is as follows : Too much emphasis must not be laid on an aver age. During a recent trial at Cornell University Experiment Station the average amount of dry matter in 125 samples of mangels, embracing ten varieties, was 11.6 per cent, the extremes between different varieties being 7.5 per cent and 16 per cent. The variation between individual roots of the same variety is equally great, being fre quently 100 per cent. In another experiment some individuals contained over 20 per cent of dry mat ter. In the case of sugar-beets, in 1904 the aver age amount of sugar obtained front one ton of beets by the factories and rasping stations in the United States was 230 pounds. From these data it is evident that the average percentage of dry mat ter contained must have been over 2 per cent greater than that given in the above table, and in many states the beets average 18 to 20 per cent dry matter, while 30 per cent with 24 per cent of sugar has been attained with individual roots.
Improvement.
During the past fifty years the amount of sugar which can be obtained from a ton of sugar-beets has been increased from about 100 or 150 pounds to 250 pounds or more, a gain of over 100 per cent. Part of this gain is due to better methods of man ufacture and part to better beets. The percentage of sugar in the beets has been increased from an average of be tween 5 and 10 per cent in 1805, to an average of 14 to 18 per cent, and 24 per cent has now been attained in individual roots, a gain due largely to a right method of selec tion. In selecting sugar-beets,a high sugar content has been insisted on and the sugar con tent of "mother beets" has been determined before they were saved for seed produc- Fig. 778. Green-top Yellow turnip.