Besides his ordinary occupations of lecturing and accompanying his pupils on their excursions into the country, he sent forth successively improved editions of several of his works, which he endeavoured to bring up to the level of his expanding knowledge. The Stockholm Academy having offered a prize, consisting of two gold medals, for the best essay on the means of improving Lapland, he composed a treatise on the subject, which received the approbation of that learned body. Although no regular cultivation could be applied to so dreary a region, he showed that considerable improvements might be made by introducing plants which grow in the mountainous districts of similar latitudes, and especially by planting trees suited to the climate. In 1759, the Imperial Academy of Sciences at Petersburg announced a premium for the best work on the confirmation or refutation of the doctrine of sexes in the vegetable kingdom. He wrote on this topic also, in which he established the fact by new and irrefragable arguments, and the reward was of course adjudged to him. The motto which he affixed to this tract was indicative of his prevailing passion: "Famam extendere factis." The celebrity of his name now attracted pupils from many parts of Europe; obtained him admission into most of the distinguished learned societies; and rendered him an object of attraction to travellers. In 1762, he was elected a foreign member of the Academy of Sciences of Paris,--a circumstance of which he was not a little proud. "It was," says he, "the greatest honour that could be conferred on a man of science, and hitherto no Swede had enjoyed it. The number of foreign members is limited to eight. The following are the names of the persons who were then invested with that dignity:--Morgagni, Bernouilli, Euler, Macclesfield, Poleni, Haller, Van Swieten, and Linnaeus."