2. ESTABLISHMENT OF THE DOCTRINE OF SEXUALITY IN PLANTS BY RUDOLPH JACOB CAMERARIUS. 1691-1694. We have seen that all that was known with regard to sexuality in plants up to 1691 was comprised in the facts related by Theophrastus concerning the date-palm, the terebinth, and the ‘malus medica,’ and in the conjectures of Millington, Grew, and Ray, while Malpighi’s views in opposition to these later authors were considered to be equally well founded. The sexuality of plants could only be raised to the rank of a scientific fact in one way, that namely of experiment; it had to be shown that no seed capable of germination could be formed without the co-operation of the pollen. All historic records concur in proving, that Camerarius was the first who attempted to solve the question in this way, and that he followed up this attempt by many other experiments. It is quite another question how the fertilising matter reaches the germ which is capable of being fertilised, and this could not be entertained till experiment had established the fact, that the pollen is absolutely indispensable to fertilisation. To Johann Christian Mikan, Professor of Botany in Prague, is due the merit of having collected the scattered and therefore almost forgotten writings of RUDOLPH JACOB CAMERARIUS[98], and published them, together with some similar works of Koelreuter, at Prague in 1797 under the title, ‘R. J. Camerarii Opuscula Botanici Argumenti.’ This book, apparently little known, will be my principal authority for the following remarks. The short preliminary communications are printed without alteration from the ninth and tenth year of the second, and from the fifth and sixth year of the third decury of the Ephemerides of the Leopoldina; the letter to Valentin, which will be noticed again further on, together with an abstract of the same and an answer of Valentin, are given according to Gmelin’s edition of 1749.