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Show 304 PHYSIOGNOMY OF PLANTS. If, then, we would attempt to solve the question spoken of in the early part of this dissertation, by giving in an approximate manner the numerical limit (le nombre limite of French mathematicians), which the whole phanerogamre now existing on the surface of the earth cannot be supposed to fall short of, we may, perhaps, find our safest guide in a comparison of the numerical ratios (which, as we have seen, may be assumed to exist between the different families of plants) with the number of species contained in herbariums and cultivated in our great botanic gardens. I have said that in 1820 the number of species contained in the herbariums of the Jardin des Plantes at Paris was already estimated at 56,000. I do not permit myself to conjecture the amount which the herbariums of England may contain; but the great Paris herbarium, which was formed with much personal sacrifice by Benjamin Delessert, and given by him for free and general use, was stated at his death to contain 86,000 species; a number almost equal to that which, as late as 1835, was conjecturally assigned by Lindley as that of all the species existing on the whole earth. (Lindley, Introduction to Botany, 2d edit. p. 504.) Few herbariums have been reckoned with care, after a complete and strict separation, and withdrawal of all mere varieties. Not a few plants contained in smaller collections are still wanting in the greater herbariums which are supposed to be general or complete. Dr. Klotzsch estimates the present entire number of phrenogamous plants in the great Royal Herbarium at Schoneberg, near Berlin, of which he is the curator, at 74,000 species. Loudon's useful work, Hortus Britannicus, gives an approximate view of all the species which are, or at no remote time have been, cultivated in British gardens: the edition of 1832 enumerates, including indigenous plants, exactly 26,660 phrenogamous species. We must not confound with this large number of plants which have grown or been cultivated at any time, and in any part of the whole British Islands, the number of living plants which can be shown at any single moment of time in any single botanic garden. In this last-named respect, the Botanic Garden of Berlin has long been regarded as one of the richest in Europe. The fame of its extraordinary riches rested formerly only on uncertain and approximate estimations; and, as my fellow-laborer and friend of many years' |