When the method of producing these skeletons became publicly known, they were soon prepared by others; some of whom made observations, which were contrary to those of Ruysch. Among these in particular were J. Bapt. Du Hamel, who, so early as the year 1727, described and illustrated with elegant engravings the interior construction of a pear[483]; Trew[484], in whose possession Keysler saw such skeletons in 1730; P. H. G. Mohring[485]; Seba[486]; Francis Nicholls[487], an Englishman; Professor Hollmann[488] at Göttingen, Ludwig[489], Walther[490], Gesner[491] and others. Nicholls seems to have been the first who split the net of an apple- or a pear-tree leaf into two equal parts, though Ruysch split a leaf of the opuntia into three, four, and even five layers, as he himself says. In the year 1748, Seligmann, an engraver, began to publish, in folio plates, figures of several leaves which he had reduced to skeletons[492]. As he thought it impossible to make drawings sufficiently correct, he took impressions from the leaves or nets themselves, with red ink, and in a manner which may be seen described in various books on the arts. Of the greater part he gave two figures, one of the upper and another of the under side. He promised also to give figures of the objects as magnified by a solar microscope; and two plates were to be delivered monthly. Seligmann however died soon after, if I am not mistaken; and a lawsuit took place between his heirs, by which the whole of the copies printed were arrested, and for this reason the work was never completed, and is to be found only in a very few libraries. Cobres says that eight pages of text, with two black and twenty-nine red copper-plates, were completed. The copy which is in the library of our university has only eight pages of text, consisting partly of a preface by C. Trew, and partly of an account of the author, printed in Latin and German opposite to each other. Trew gives a history of the physiology of plants and of leaf-skeletons; and Seligmann treats on the methods of preparing the latter. The number of the plates however is greater than that assigned by Cobres. The copy which is now before me contains thirty-three plates, printed in red; and besides these, two plates in black, with figures of the objects magnified. Of the second plate in red, there is a duplicate with this title, “Leaves of a bergamot pear-tree, the fruit of which is mild;” but the figures in both are not the same; and it appears that the author considered one of the plates as defective, and therefore gave another. The leaves represented in the plates are those of the orange-tree, lemon-tree, shaddock-tree, butcher’s-broom, walnut-tree, pear-tree, laurel, lime-tree, ivy, medlar, chestnut-tree, maple-tree, holly, willow, white hawthorn, &c.