Johann Jakob Dillenius, a German botanist, born in Darmstadt in 1687, died in Oxford, April 2, 1747. His grandfather was called Dill and his father Dillen, which the son Latinized into Dillenius. He studied at the university of Giessen, and was received into the society of " Inquirers into Nature," under whose auspices he published a "Dissertation upon the Plants of America naturalized in Europe;" a "Treatise upon Coffee," with an account of the substances which might displace it, giving the preference to burnt rice; and a volume of "Observations upon the Mode of Development of Ferns and Mosses," in which he confirmed the theory of different sexes in plants. He first obtained a reputation among naturalists by his Catalogus Plantarum circa Gissam nascentium, published in 1719. William Sherard, a scientific English traveller, persuaded Dillenius to leave Germany for England. He arrived in London in 1721, and had a fine garden at El-tham placed at his disposition by James Sherard, a brother of William. He edited an enlarged edition of Kay's " Synopsis of British Plants," with engravings of his own.

In 1728 William Sherard died, and founded by his will a chair of botany at Oxford, to which Dillenius was appointed, who in 1732 published his Hortus Elthamensis, containing not only descriptions of plants arranged in alphabetical order, but also 324 plates engraved by himself. This work was enthusiastically received by his contemporaries, among others by Linnaeus, then commencing his labors. In 1741 he published his Historia Muscoram, which places him in the first rank of the botanists of the last century. He was more than 20 years in collecting the materials of this work. The plates (numbering 85) and the descriptions were all by his own hand. He published no subsequent work, but many of his drawings and collections are preserved in the Sherardian museum at Oxford. Linnaeus dedicated to him a magnificent genus of plants of tropical India, which is the type of the family of the Dilleniaceoe.