Stalk.—The industrial value of the cane-stalk depends on a great variety of features, all related to the amount and nature of the saccharine matter that can be extracted at a given cost, and the ability of the stalk to reproduce itself with its properties unimpaired. This subject is very com plicated, and only a brief outline can be undertaken. Two main features will be discussed : (1) The amount and nature of the saccharine matter ; (2) The struc ture of the stalk. These two are closely related.
(1) Amount and nature of the saccharine matter.— The saccharine matter is distributed in the stalk according to a definite law which may be roughly expressed by saying that it reaches its maximum near the middle of the stalk and is at a minimum near the ends, the decrease being least toward the ground and greatest near the top. At a certain period of growth, varying widely with climate, the total saccharine matter reaches a maximum. This is the ripening period, and, of course, the period at whose termination the cane should be crushed. Judging this stage is a crucial test of the grower's skill. Not only does it vary with the gen eral climate, but also with the particular season and with the soil and the variety. In general it may be said that the ripening is governed by the temperature and the sunlight. Two plantations having the same conditions otherwise, but the one subject to more cloud shadow than the other, will vary in the richness of the juices extracted from the cane. In a similar way any change in the tem perature will work a like change in the yield of sugar. One plantation, irrigated with cold spring water derived from high mountains, will vary materially from another irrigated with rain-water brought from a distance in open ditches, and there fore applied at a higher temperature.
After reaching their maximum, the extractable saccharine matters decrease as the cane grows older and begins to form its inflorescence. In fact, it is for the work of flowering that the cane plant stores up saccharine matter. In the effort to har vest the cane at its maximum saccharine content, the planter is aided by the chemist who makes analyses of sample stalks of the crop. This test, however, is not always resorted to, as the planter learns by experience to judge the ripeness of the cane by its outward appearance, i. e., its color, the stage of its inflorescence, and the like.
Because of the expensiveness of the modern mill, it is necessary for economic reasons to prolong the crushing season as much as possible, and for this reason the planter resorts to various methods to prolong the ripening of his fields in such a way that they reach their maximum sugar yield in suc cession during the crushing season, which may thus last for several months. By using several varieties
of differing degrees of earliness, by varying the planting season, by taking advantage of low land and high land and other natural conditions, it is possible to extend the crushing season so as to get a maximum result from the capital invested in the mill and from the laboring force of the plantation. As we shall see later (page 602), the time of ripen ing, i. e., the distribution of the sugar in time, as well as the distribution of the sugar in the stalk, have much to do with the selection and preparation of seed-cane.
The kind of sugar present in the cane, as well as the amount of it, determines its industrial vales. The property that makes the saccharine substance of the greatest industrial value at the present time, is that of its being extractable by the known processes of crushing, concentra tion and crystallization. Preeminent among the extractable saccharine substances of this nature is sucrose. This crystallises out as "cane-sugar," and is the same substance as that obtained from sugar-beets and a variety of other plants. In fact, from a practical point of view, at the present time, we may say that the amount of extractable sucrose determines the value of the cane more than any other factor except that of ability of the cane economically to reproduce itself with this sugar content unimpaired. We must not forget in this connection, however, that the ease with which the sugar can be extracted is also an important factor. The presence of saccharine matters other than sucrose is deprecated by planters because their pres ence generally indicates a lowering of the sucrose, the energy of the plant having been consumed in producing sugar or saccharine matter that is not extractable, in place of a certain amount of sucrose that might have been produced. The extractability of the sucrose depends to a certain extent on the absence of certain organic substances which tend to cause the sucrose so to change its molecular form as to become unextractable or of less value. To a large extent, these difficulties are surmounted by the application of hydrate of lime to the juice as soon as possible after it is removed from the cane.