Having gone with Cliffort to Amsterdam, and afterwards to Leyden, he visited among others his friend Van Royen, professor of botany, who having made proposals of marriage to Miss Boerhaave, the sole heiress of the great physician, had been rejected, and therefore vowed hostility to the family. The botanic garden there had been arranged and described agreeably to Boerhaave's method; but the other now resolved to alter the disposition, and adopt the system of Linnaeus. He accordingly offered him a salary of eight hundred florins, if he would live with him, and assist in the execution of this scheme. Influenced by respect for his deceased friend, he would not countenance the alteration, although he devised a plan by which neither his benefactor nor himself should receive the honour. He remained with Van Royen, classed the plants after a principle of his own invention, and drew up a catalogue of them, which was published in the name of that teacher. The next work which he printed was produced by the genius and industry of Artedi. When he resided at Leyden, previous to his going to Hartecamp, he had the pleasure of meeting this friend of his youth, who had left Sweden in 1734, and gone to England to prosecute his scientific labours. From thence he went to Holland for the purpose of obtaining his degree, which he was unable to accomplish on account of his extreme poverty. Linnaeus recommended him to Seba, an apothecary at Amsterdam, and author of a large work on natural history, who received him as his assistant. But soon after, returning home in a dark night, he fell into a canal and was drowned. His countryman had the melancholy satisfaction of depositing his remains in the grave; and having induced Cliffort to purchase his manuscripts, which were detained for debt, he arranged and committed them to the press. This tract, in his opinion, was the best that had appeared on the subject of fishes. He also published his own Classes Plantarum, in which he presented a general view of all the botanical systems that had been previously proposed. His ambition was now on the point of being attained. Not only were his works received with approbation, but his principles had been adopted by several teachers. He had also formed connexions in Holland which promised to be of the greatest advantage to him; and the Dutch, desirous of securing his services, proposed that he should make a botanical voyage to the Cape of Good Hope, with the promise of a professorship on his return.