400 History of the Sexual Theory. [BOOK in.

One experiment only is mentioned, but not the person by whom it was made. We read at p. 99 that in the year 1723 in the garden of Stenbrohuld, the male flowers of a gourd in bloom were daily removed, and that no fruit was formed. Soon after allusion is made to the artifices used by gardeners to obtain hybrid varieties of tulips and cabbage, but the matter is treated rather as agreeable trifling. In the third volume of the Amoenitates of the year 1764, in which Koelreuter's first enquiries into hybridisation had been already published, we find a dissertation on hybrids by Haartman, which was cer- tainly written as early as 1751. In this treatise the necessary existence of hybrid forms is concluded from philosophic principles, as Linnaeus had deduced sexuality from similar principles ; no experiments are made, but certain forms are arbitrarily assumed to be hybrids ; a Veronica spuria gathered in the garden at Upsala in 1750 is asserted to be the product of Veronica maritima as the mother and of Veronica offici- nalis as the father, but the only reason for assigning the paternity to the latter plant is that it grew close by. We find also a Delphinium hybridum stated on similar grounds to be the offspring of Delphinium elatum fertilised by Aconi- tum napellus, and a Saponaria hybrida to have arisen from the pollination of Saponaria officinalis by a Gentiana ; and we are told among other things that Actaea spicata alba is the offspring of Actaea spicata nigra fertilised by Rhus toxicoden- dron. It is obvious that in all this there was no observation of decisive facts, but simple conclusions from arbitrary pre- mises.

We conclude therefore that neither Linnaeus nor his disciples in the interval that elapsed between the labours of Camerarius and Koelreuter contributed a single new or valid proof to the establishment of the fact, that there is a sexual difference in plants and that hybrids are formed be- tween different species ; and if many later botanists talked

of the great services rendered by Linnaeus to the sexual