1370. To the secreted saps belong the coloured milky juices present in particular vessels, and consisting for the most part of water with resins, as in the celandine and spurge. The particular saps, especially those of the fruits, are very composite, consisting for the most part either of mucus, sugar and acids, or occasionally of gelatine and albumen. Solid compound matters are almost universally made up of flour, which consists principally of starch and gum; or they are furthermore mucus in the roots and seeds. The excreted or separated matters, which no longer interpose in the vegetable process, are the etherial oils, resins, fixed oils, colouring matters, poisonous substances, gum, tannin, nectar-juices, and even water. B. _Preliminary Events._ a. WROUGHT BY EXTERNAL INFLUENCE. 1371. The influence of the elements produces different phenomena in the plant. I have felt constantly more inclined to consider, that not merely the descent of the root, but even the ascent of the stalk was simply to be viewed as a mechanical event, or one forsooth effected by gravity. The roots obey under all circumstances the gravity and would grow as far as the centre of the earth, were they to meet with no impediment; and there they would follow the revolution of the earth, and consequently become spirally convoluted upon themselves. It is almost beyond doubt that the water, which sinks downwards and, as it were like that in stalactites, invariably rigidifies or hardens at the radical capillaries, is heavier in the root. The cause of this greater weight depends upon the mucus not being decomposed. 1372. The straight ascent of the stalk also depends upon nothing else than gravity. The upper drops of mucus become lighter by means of greater heat and by decomposition in light and air, and they are therefore compressed by the heavier in the upward direction. It is always such a small drop upon the summit, which hardens into its uppermost cell. The stalk, therefore, grows upwards through the same forces and in the same manner, as the air-bubbles ascend in a glass of beer. The cause of their becoming lighter resides certainly in the vital process, which nevertheless effects in this respect nothing else than the extension or increase; but yet the cause of the ascent is naught else than the gravity.