On the Roots of the Sugar-cane. By HY. LING ROTH. [Read before the Royal Society of N.S. W., 3 October, 1883.] THE knowledge of the growth of cane roots being important to planters, the following experiments were made at Foulden Plantation, Mackay (Queensland) with a view of gaining some information on this point. A. On 20th November, 1882, a cask 30 inches deep, with the bottom knocked out, and 17 to 22 inches in diameter, was filled with manured garden soil well mixed down to 12 inches from the bottom, and sunk into the ground so that the top of the cask was on a level with the surrounding soil. In the cask were planted, 4 inches deep, two Rose-bamboo plants with three good eyes in each. B. On the same date were planted a few feet distant from the above, two plants of the same variety of cane, with a like number of eyes and placed at the same depth. This plot trenched 4 feet square and 20 to 22 inches deep. The soil was a light black loam for the first 15 inches, then a heavier brown loam, which at 40 inches depth had merged into river sand. As far as has yet been ascertained, this sand extends down to beyond 6 feet. This plot was not manured. The cask was raised on 16th August and knocked to pieces, leaving a compact mass of roots binding the earth firmly together. The soil was removed by means of washing with water, but the roots were so fragile that in spite of every precaution many were broken off; in fact, from the quantity of rootlets collected in the water afterwards, I should say that fully one-sixth were dissevered. Plate I will show the dense character of these roots. Some of these roots had spread out laterally, and not being able to extend beyond the cask had gone downwards; other roots, again, had gone down at once. As it was not imagined that any roots would have descended to a greater depth than 30 inches (the depth of the cask) no precautions were taken to prevent the sundering of any roots which penetrated below that depth. I afterwards found that almost all the roots had thrust themselves into the sand below the cask. The cane had been planted very late in the season, but had grown fairly well; the diameter of the canes reached 11⁄2 in., but the colour of the leaves was pale and unhealthy, having become and remained so after five months growth, owing to the restrictions on the spreading of the roots by the cask. When taken out of the cask there appeared to be more roots than soil, and examined under the microscope, the fine roothairs (trichomes) showed a diameter of one 250th to one 275th of an inch. Where the roots had come across a lump of manure they had formed a compact net-work. The roots of B were raised on 20th August, 1883. In digging out the roots of this cane, which was grown under perfectly normal conditions, ample room was allowed for the lateral roots, which were found to spread to a distance of over 3 feet. Having found these, I dug down and gradually approached nearer, until having excavated enough soil at a depth of 5 feet, I began to look for the tips of descending roots. The deepest root thus touched was at a depth of 42 feet, being 5 feet 1 inches long from its departure from the cane plant to its tip in the sand (Plate II, fig. 1). Another root (Plate II, fig. 2*) was 3 feet 10 inches long, and also grew almost perpendicularly downwards. Starting from above again, the roots on the surface were not quite so dense as those in the cask, but were very close to a depth of nearly 2 feet, below which depth they thinned considerably. The cane, although, like the other, planted late, was fairly grown, with a good healthy colour in the leaves, about 18 inches higher than the cane in the cask, and the canes from 13 to 17 inches in diameter. In Plate II the tip of the long root (fig. 1) was broken off in removal; but fig. 2 shows the tip intact; its diameter at the broadest part was 5-16th of an inch. Nos. 3, 5, and 6 are tips of roots found at various depths (No. 6 as deep as No. 2); No. 4 are the surface or upper roots, the same as shown in Plate I. The two root stems Nos. 1 and 2 look very naked; in reality they were not so, but in tracing them back to the planted pieces of cane, all the branches were broken off-their points of disconnection are plainly discernible; the rootlets were exceedingly brittle towards the lower end, and I feared that by attempting too much I might lose all. No roots tipped like Nos. 1 and 5 were found except with a downward tendency, that is to say, I found no lateral roots tipped like those. This, however, does not prove that the cane has two distinct classes of roots, for being very fragile, and being in the loam, which is not so easily disconnected as the sand, I may have missed them in consequence of the tips remaining in the soil. In the fields, young cane which has sprouted to only 6 to 10 inches above ground will have fine roots going to a depth of 30 inches. All this would seem to indicate that cane like other * To obtain a thorough idea of the roots, this Plate should be examined through a magnifying glass; the tip of root (fig. 2) would thus be seen to advantage. plants requires plenty of room for the natural spread of its roots. Where there was plenty of food and the soil was loose enough to allow of the roots to penetrate with ease, there the roots were thickest; where the soil was not in that condition, or there was no great quantity of food, there the roots were thinnest.* It is much to be regretted that so few writers on the sugar-cane should have given any attention to the roots. In a new work on sugar-growing, † a totally erroneous impression concerning the roots of the cane is conveyed to the mind of the reader. On page 15 a drawing of a cane is given with its so-called root, but the cane, as drawn, only goes so far as to give the point of its attachment to the parent plant-cane, and does not show either the root-stems or the roots. On page 19 another drawing, intended to explain how cane spreads, is also misleading; such a growth is quite abnormal, and might appear once in a man's lifetime. Both these illustrations are taken from "The Sugar-cane," written by Porter, and published in 1843. In that work, p. 14, Porter says: "The roots are very slender and almost cylindrical; they are never more than a foot in length; a few short fibres appear at their extremities." These words are copied verbatim by the authors of the new work, and how mistaken they are I have shown above. The only work I have met with where cane is really correctly pictured is a Report by M. Ch. L. Fleischmann. ‡ In that Report, fig. 29a presents the underground attachment of a young cane with its rootlets. This drawing is correct so far as it goes, but if more rootlets had been figured a truer idea could be formed. DISCUSSION. PROF. LIVERSIDGE stated that he saw at Maryborough, in Queensland, roots of the sugar-cane extending down from 8 to 10 feet, where they had been exposed by the cutting away of a bank, and he had been informed by planters that they had traced roots down to a depth of even 12 to 15 feet in light alluvial soil. * Compare these results with those of Prof. Nobbe, Versuch Station IV, p. 212, quoted by S. W. Johnson. "Sugar-growing and Refining," by Lock, Wigner, and Harland, London, 1882. Annual Report of the Commissioner of Patents for 1848, Washington, 1849. This Report also contains some well-drawn illustrations of microscopic sections of the sugar-cane by M. Corda, Professor at the University of Prague in 1848. [Three diagrams.] |