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Show 318 COW-TREES. in an old plant amounts to nearly two-thirds of the entire weight of the plant. When recent, it very much resembles milk, and when consolidated it ts Indian rubber. , It is not very clearly ascertained to which of the two families the Palo de vacca, or cow-tree of South .America, belongs; but the people resort to that tree, fetch the juice in pitchers, and use it for the same purposes as animal milk. Nor is it a little curious that, in those parts of the world where, on account of the parching up of the grass, the milk of domestic ammals is not so easily procured as in more tern perate climates, there should be an abundant, and by no means a bad, substitute in the juices of trees. But besides their eatable juices, these plants have a very deleterious principle, which in some of the species is a very virulent poison. That principle is Strychnia, so called from bei11g first found in the kernels of the Strychnos nux vomica and St1·ychnos ignatiana; but it is also found in the Upas, and in other species: and it is not a little remarkable, that while some of the species of Strychnos are so deadly, others are valuable medicines. These coincidences in some respects, and differences in others, should teach us to be cautious in not ~eneralizing to any of those artificial tribes of orgaruzed being any property which we have discovered only in some members of that tribe. The products of organization are quite different from both mechanical and chymical results. We cannot repeat one of them, and therefore we can never safely say that any one of them has a property, unless that property has actually been discovered in it. Still the poison, or the other active matter that may be in the plant, is well worthy of our study; because, generally speaking, it is in the plant itself, and not in the food of the plant. In whatever part of the plant it may ultimately be found, whether in the root, as in the jatropha; in the juice, as in thA POISON OF PLANTS. 319 spurges; in fo~licle~, with prick1es on the hark, as ~~ the uettl? tnb~; m the oil of the seeds, as in the ywlen ; or m th~u substances, as in nux vomica-it IS always found m one part of the plant when in the embry~ state. That_ part is the embryo itself, when the hal.Ht of_ the plant IS such that that is considerably developed ~n the seed. When that is not the case ·the most ~1rulent property is in the tunics or coats~ and that IS the case also with roots~ and it is th~ same whatever may be the nature of the poison. In the p~1lp o~ the peach there is not a trace of that , prussic acid which scents the flower and :flavours the kernel; the pulp of the yew-berry is harmless and probably so are th~ cotyledons, if the embry~ were removed, as tlu~t IS the case with many of the seeds of the .EU:phorbtacea:, and other tribes. In the potato, the J?Ol~<?nous qualitr, w~ich, though not very ~trong1 IS stll~ a pmson, IS chiefly in the tunic ?r skm, or lll!f!ledtately under it; and the same is, tn all probabi~Ity, th~ case in jatropha. Even the co~mon tnrmp, whiCh belongs to an order of whiCh proba~ly none are_ poisonous, though some are very acnd, has the rmd of the bulb far more pungent than the bulb itself. The uses of the plant~ classed under the fig tribe and those resemblmg It, are exceedingly varied. Many of them, as has_ bem~ stated, furnish food, and many more, from t~eir active nature, are medicinal and othe!s form articles_ of clothing, either through the_ medmm of _somethmg else, or directly. The wh1te mul~erry IS the principal food of those silkworms whiC~ every year spin so great a quantity of the most ?eh~ate and also the most beautiful substance which _Is er:n:~Ioyed in the loom. The paper ~ulberry, 'Yh1eh, If It does not agree with the order 111 all partiCulars ~and the agreement or disagreement of plants ~Ith an order or a genus in any s~ste~ depend_s 111_ a _great measure upon that system), agrees with 1t m many, is used, as the name |