The preceding experiments give us an explanation of the curious phenomena exhibited by so-called creeping salts. A saline solution left at the bottom of a vessel will sometimes be found after some months to have crept up to the top of the vessel. Cellular partitions formed in this way will be found extending from the bottom to the top of the vessel, and not only so, but the whole of the remaining liquid will be imprisoned in the upper cells. [Illustration: FIG. 38.--Osmotic growth produced by sowing a mixture of CaCl_2 and MnCl_2 in a solution of alkaline carbonate, phosphate, and silicate. The stem and terminal organs are of different colours. (One-third of the natural size.)] [Illustration: FIG. 39.--An osmotic growth photographed by transverse light to show the construction of the terminal organs.] _Assimilation and Excretion._--Like a living being, an osmotic growth absorbs nutriment from the medium in which it grows, and this nutriment it assimilates and organizes. If we compare the weight of an osmotic growth with that of the mineral fragment which produced it, we shall find that the mineral seed has increased many hundred times in weight. Similarly, if we weigh the liquid before and after the experiment, we shall find that it has lost an equivalent weight. The absorbed substance of an osmotic production must also undergo chemical transformation before it can be assimilated--that is, before it can form part of the growth. Calcium chloride, for example, growing in a solution of potassium {130} carbonate, is transformed into calcium carbonate. CaCl_2 + K_2CO_3 = CaCO_3 + 2KCl. Thus an osmotic growth can make a choice between the substances offered to it, rejecting the potassium of the nutrient liquid, and absorbing water and the radical CO_3, while at the same time it eliminates and excretes {131} chlorine, which may be found in the nutrient liquid after the reaction. Of all the ordinary physical forces, osmotic pressure and osmosis alone appear to possess this remarkable power of organization and morphogenesis. It is a matter of surprise that this peculiar faculty has hitherto remained almost unsuspected. [Illustration: FIG. 40.--Osmotic growth in a solution of KNO_3, showing spine-like organs.] _Osmotic Growths._--If we sow fragments of calcium chloride in solutions of the alkaline carbonates, phosphates, or silicates, we obtain a wonderful variety of filiform and linear growths which may attain to a height of 30 or 40 centimetres. Some are so flexible that the stems bend, falling in curves around the centre of growth, like leaves of grass. If we dilute this same liquid, as it becomes less concentrated the growths are more curved, ramified, dendritic, like those of trees or corals. [Illustration: FIG. 41.--Terminal organs like catkins, developing in a solution of ammonium chloride.]