36 PLANT HYBRIDIZATION BEFORE MENDEL 



tory in the University of Karlsruhe. At Sulz, in 1760, Kolreuter 

 produced the first plant hybrid obtained in a scientific experiment. 

 Kolreuter's most important papers, his "Vorlaufige Nachricht," 

 and its three 'Tortsetzungen" (1), cover a reported period from 

 1760 to 1766. In the former year, Kolreuter secured his first hy- 

 brid, Nicotiana paniculata 9 y<( N. rustica 5 . The experiments 

 during the following six years, numbering 65 definitely described, 

 covered crosses involving 13 genera and 54 species. Before tak- 

 ing up these experiments in detail, and especially those of ge- 

 netic interest, it will be well to deal with Kolreuter's views or 

 conclusions with respect to the fertilization process and hybridiza- 

 tion. In the first place, it will be understood that Kolreuter worked 

 with the microscope. Sprengel indeed remarks, regarding the for- 

 mer's study of pollination in Asclepias, that some of the observa- 

 tions therein he himself had not been able to make. "Da ich kein 

 so gutes Vergrosserungsglas zur Hand gehabt habe, als Kolreu- 

 ter." (2, 1 : 165.) It is desirable also to remember that Kolreuter 

 not only carried on his investigations upon hybrids, but made 

 extensive observations upon pollination. Indeed it is possible 

 that Sprengel's title for his work "Das entdeckte Geheimniss 

 der Natur," (1793) may have been suggested by Kolreuter's 

 remark, "Gewiss ein jeder anderer, der vor mir diese Betracht- 

 ungen angestellet hatte, wiirde sie langst entdeckt, und sich 

 und alien Naturforschern von diesem Geheimnisse der Natur den 

 Vorhang langst weggezogen haben." (p. 21.) Kolreuter himself 

 alludes to his use of a "Vergrosserungsglas," in his search for the 

 stigmatic surfaces in Iris (i, p. 22), and in the examination of 

 the pollen in his first Nicotiana hybrid, (p. 31.) 



Kolreuter considers that the pollen is a collection of organic 

 particles, which have a definite form in every plant. In structure, 

 the pollen grain consists of an outer thick membrane or rather 

 of a hard and elastic shell, upon which, at equal distances apart, 

 are found the "excretion-canals" and openings for escape of the 

 male fertilizing material. In the species in which the pollen grains 

 are beset with projections, these excretion-canals are in the pro- 

 jections themselves, being found at their apices. Within the elas- 

 tic shell, there is stated to be a netlike mass of vascular fibres 

 which, in some species, is arranged in almost regular hexagonal 

 fashion; in others, in some other more or less regular way. 



