The homogeneousness of the tragacanth mucilage in cold solution comes naturally after the size is five or six days old, because within this time fermentation of lactic acid occurs, which opens the cells of the small granules of starch while at the same time boiling heat has an immediate result in the same direction. As soon as these cells are opened the formation of acids of the sugary parts and the fermentation of lactic acid of the starch contained in the size take place as fast as in any other variety of size, hence the size of tragacanth has no superiority over any other, besides the best, or picked-leaf tragacanth of Smyrna costs about four times the price of the best Carrageen. For the preparation of the size, take 3 ounces of tragacanth, pour two quarts of water over it, leave it stand for 24 hours, then stir well and leave it standing for 12 hours more, repeat this until the homogeneous thick mucilage has been produced, then add 4 quarts of water, again stir it up well and filter it and the size is ready for the marbling process. For tragacanth size, colors of great consistency, mostly fine earth colors are the best. They must be ground exceedingly well and very little ox-gall is to be added. But as these earth colors lack in the power to spread out and in divisibility, a characteristic of colors prepared for carrageen size, and as they never will have such fineness and smoothness, always appearing rugged, it is impossible for me to recommend gum tragacanth for the preparation of size. I must mention further an effect, which earth colors exert on tragacanth size, viz., that they can be used on paper not prepared with alum, without running, while this is not the case with colors, which were prepared for the Carrageen size. In another chapter upon ox-gall I shall explain why the colors used with Carrageen size must be transferred on alum paper. Salep, Plantago-Psyllium. SALEP, PLANTAGO-PSYLLIUM (Flea-bane) AND THE OTHER GELATINOUS BODIES. Radix salep are called the dried tubers of several species of orchids, they are round, quite flat, yellowish white, horn-like, semi-diaphanous, very hard and without taste or smell. Formerly salep was imported mostly from Persia, but now the tubers of orchids grown at home are collected and do not in any way differ from those coming from Asia. They contain a good quantity of gum and on that account are used for finishing silks and for medicinal purposes. It is sold ground, or as powder and can be bought at every drug-store. As marbling size, salep possesses very excellent properties, similar to carrageen moss, but its high price prohibits its general application. In preparing size, use, to 6 quarts of water 2-1/2 ounces of powdered salep which must be well boiled for a long period so that it may become entirely dissolved. After standing 24 hours, it can be used in the same way, as carrageen size.