184 Morphology and Systematic Botany under [BookI. 



doubts respecting matters of detail. Hofmeister's researches 

 in morphology and embryology (' Vergleichende Untersuch- 

 ungen,' 185 1) threw an entirely new light on the relations of 

 affinity between the great groups in the vegetable kingdom, 

 and were leading more and more to the view, that there must 

 be some special peculiarity in the question of the constancy 

 of organic forms. But the idea of evolution in the vegetable 

 kingdom was brought more distinctly home to men's minds by 

 palaeontological researches; Sternberg (1820-1838), Brong- 

 niart (1828-1837), Goeppert (1837-1845), and Corda (1845) 

 made the flora of former ages the subject of careful study, 

 and compared fossil plants with living allied forms. Unger 

 especially, while advancing the knowledge of the structure 

 of cells and of vegetable anatomy and physiology, and generally 

 taking a prominent part in the development of the new botany, 

 applied the results of its investigations to the examination 

 of primeval vegetation, and showed the morphological and 

 systematic relations between past and existing floras. After 

 twenty years of preliminary study he declared distinctly in 

 1852, that the immutability of species is an illusion, that the 

 new species which have made their appearance in geological 

 periods are organically connected, the younger having arisen 

 from the elder 1 . It was shown in the former chapter, how 

 about the same time the leading representative of idealistic 

 views, Alexander Braun, was driven to the hypothesis, though 

 in a more indefinite form, of an evolution of the vegetable 

 kingdom : and in the year that Darwin's book on the origin 

 of species appeared, Nageli ( ' Beitrage,' ii. p. 34) wrote: — 

 ' External reasons, supplied by the comparison of the floras of 

 successive geological periods, and internal reasons given in 

 physiological and morphological laws of development and 

 in the variability of the species, leave scarcely a doubt that 

 species have proceeded one from another.' 



1 See A. Bayer, 'Leben und Wirken F. Unger's,' Gratz (1872), p. 52. 



