In the Bulletin for March, notes were published on the onion, and it was stated that seed was being obtained through Sir D. Morris, from Teneriffe. This seed, both of red and white onions, has arrived, and will be distributed to applicants at the rate of three-pence per ounce or four shillings per pound. Application, accompanied by a remittance, should be addressed to the Director of Public Gardens, Kingston, P.O.

BEETLE PESTS.

LEAF EATING BEETLE.

A correspondent sent specimens of a beetle about three-quarters of an inch long, of a shining black colour, complaining that it was "very destructive to rose trees and several other plants, not allowing any buds, flowers, or young leaves to come out, before they are seized on and eaten off."

Paris green was recommended as a remedy, to be applied as advised in the Bulletin for July.

The specimens were referred to Mr. E. S. Panton, Curator of the Museum, who writes :-" The beetles are a very destructive species of Lamellicornes (Antichira meridionalis). They often descend in countless numbers on different trees and plants at this time of year, sometimes entirely defoliating them. Trees that are usually attacked are the Poinciana and Trumpet. At this moment they are crowding on some Trumpet trees shading my coffee here. I find the larva feeds on the decayed wood of the wild Calabash.

BRANCH CUTTING BEETLE.

Revd. George Davidson, Arcadia, Chapelton, writes:

"Accompanying this I send you for inspection a bit of stick of the Beechwood. You will observe one end has apparently been cut by a saw. I have recently found many such pieces some very much thicker but all bearing the same appearance. The cuttings are not confined to any one particular kind of tree. I yesterday saw two much thicker branches of the tamarind tree. I am curious to know what is the insect or reptile responsible for this work. Some of the peasantry attribute it to a large lizard known to them as "Dom Sawyer." Your opinion will be greatly appreciated."

The insect responsible is a beetle* which lays its egg in a branch near the end, and gnaws the wood right round, so that the end dies and falls off. The larva feeds on the dead wood, and only emerges when it transforms into the perfect insect. The remedy is to collect and burn all the dead girdled branches which contain larvæ, and to destroy all the beetles when found on the trees.

THE MANUFACTURE OF STARCH FROM
THE POTATO IN GERMANY.

By H. H. COUSINS, M.A., F.C.S., Island Chemist.

As sugar cane is to the sugar beet so is the tropical cassava plant to the potato of temperate climates. To establish a cassava starch industry in Jamaica on a sound basis it will be necessary to conduct the cultivation and process of manufacture with as efficient methods as those now obtaining in the rival potato starch industry so as to obtain the full benefit of the superior starch producing powers of the tropical plant.

I have therefore thought that it might be of interest to those who are considering cassava as a possible crop for Jamaica to give some general idea of the potato starch industry as at present carried on in Germany.

THE POTATO AS A SOURCE OF STARCH.

The season of growth greatly affects both the yield of tubers and the starch content. There is also a very great variation in the starch value of different varieties of potato and again between in-. dividual tubers of the same variety.

The late Professor Maercker, who played the chief part in establishing the potato industry of Germany on a firm agricultural and technical basis, found individual tubers containing as much as 29 per cent. of starch and in a warm season of favourable growth he frequently recorded the analysis of samples containing 25 to 27 per cent. of starch. Maercker found, however, that while some tubers gave this high amount of starch, others from the same * Oncideres pustulata.

crop grown under identical conditions failed to show more than 16 per cent. of starch. As a rule the small tubers were found to contain less starch than the larger ones.

The richer the seed potatoes in starch, the higher the average starch content of the resulting crop.

Very great progress and development has been achieved in the production of potatoes suitable for starch production by selection and the raising of seedlings from selected parents.

The starch content of the cultivated potato has been raised quite 40 per cent. over that of the old standard by this means and varieties of high agricultural productivity and vigour have been placed at the disposal of the growers.

The period of growth of the German potato crop is about five months, and as it requires a considerable amount of plant food in this short space of time the soil must be in high condition and a liberal manuring must be maintained to secure good crops.

The value of a potato does not depend upon its content of starch alone: the skin, the "eyes," the fibre and especially the structure of the starch granules are of the highest importance from the point of view of the starch manufacturer.

A careful study of the potato has shown that it is highly important for the starch factory to secure ripe tubers since these give the largest yield of first quality starch.

The potato crop is liable to various fungoid diseases of the most serious character and the cultivator has to take full precautions against disease.

In certain seasons the losses from disease are very great.

The cassava crop as grown in Jamaica should have a great advantage in its immunity from serious diseases and pests and the unrestricted season of growth and harvest.

* A verage of 38 varieties of German Potatos by Morgen.
† Average of 21 varieties of Jamaican Cassava by Cousins.

Average.

Max.

Min.

Average.

THE PROCESS OF MANUFACTURE.

The work of a starch factory may be summarised as follows:

(1.) Potatoes are brought by train or water and are stored in heaps, cellars or sheds.

If the factory is buying potatoes, determinations of the percentage of adherent earth and of starch are made to regulate the price payable.

(2.) The potato washer consist of a series of troughs in which the tubers are slowly stirred under water to remove the adherent dirt. The tubers are then removed and sprayed with clean water and are then ready for

(3.) The pulping process.-The potato is composed of a mass of small cells in which the starch grains are locked up. The object to be attained in the pulping process, therefore, is that of as complete a disintegration of the cellular mass as possible.

This is carried out by means of a revolving drum armed with sharp teeth attached like narrow saws parallel to the axis upon which the drum revolves.

A velocity of 900-1,200 revolutions per minute is imparted to the drum by suitable machinery.

The potatoes falling against this revolving drum are rapidly reduced to a fine-grained, foaming reddish pulp.

It is usual to moisten the tubers with an equal weight of water to facilitate the pulping.

The pulp consists of the juice of the tubers, free starch granules, fibre and cells still unbroken. In small factories the fibre and whole cells are removed by sieves and after drying used as cattle food, in larger concerns this product is separated and ground up in a mill so as to liberate more starch. In no case can all the starch in the tubers be liberated.

(4) Washing out the Starch.-The separation of the starch from the juices and the fibre is carried out by a system of sieves.

Flat sieves are usually constructed so that an engine can be used to shake them to and fro or else a mechanical arrangement of moving brushes is employed to work the starch through the meshes. Sometimes revolving cylinders of wire gauze are used.

1

The coarser sieves have a mesh of inch, the fine sieves are made of the finest wire gauze or of No. 5 silk gauze.

Careful attention to the sieves is one of the first essentials for ensuring a high class product.

The starch "milk" obtained from the last sieve contains, besides

the juices of the tubers and the starch granules, a certain amount of mud and fine particles of fibre and cell-tissue.

Since the sand, starch and the cell-particles are heavier than water they gradually sink and the remaining impurities can be removed by drawing off the liquid. This process is carried out either by sedimentation direct or by a process of running water.

In the former process, vessels 3 or 4 feet in height are used. After 8 or 10 hours the starch has settled, the water is run off and the starch dug out from the bottom with spades.

In the flooding system, a stream of starch water flows over a level wooden channel 5 feet wide, 18 inches deep and 60 or more feet in length.

By this means the greater portion of the starch s purer state than in the sedimentary process, while th smaller starch granules pass off with the impurities. from the outflow is subsequently recovered by letting the liqu stand in suitable vessels.

The crude starch is a yellowish, brown or red mass which should be quite hard and firm.

This first product is far from pure and is now passed through the process of

(6) Purification. This is generally carried out by working up the crude starch into a 'milk' of about 18° Beaumé and allowing it to settle. After 6 to 10 hours the starch has settled as a hard, white mass with a superficial stratum of a brown. slimy mass of impure starch.

In most cases some treatment with sulphurous acid or bleaching powder is carried out at this stage to whiten the final product. The impure surface layer is removed for further treatment while the lower deposit is secured as the first product of the factory.

Special processes for purifying the precipitated starch from the waste waters and the slimy starch above described are resorted to and a very considerable proportion of the starch set free is finally secured as "superior" and "seconds."

(8) Drying the Starch. This is generally carried out first by centrifugals and then in special drying rooms.

The Bye-Products.

(a) The pulp.-This contains 88 to 97 per cent. of water. By pressure the moisture can be reduced to about 25 per cent. and it can then be fed to cattle direct or is dried by artificial heat and sold as a dry cattle food.

(b) The waste water.-This contains much plant food and can be best used for the irrigation of the lands in the close vicinity of the factory.

The returns from a German starch factory.

The following tables given by Dr. O. Saare* represent the efficiency of starch manufacture in Germany under various conditions. *Die Fabrikation der Kartoffel Stärke.