LIXXEAN SOCIETY OF LONDON. 23 



him to the right conclusion, though it must be .idinitted that 

 Others had already been more fortunate. Brougniart, however, 

 quite rightly interpreted the structure of Psaroains, as regards 

 the distinction between the stem and the surrounding zone of 

 roots. 



The volume comes to a sudden end in the middle of a sentence 

 on p. 72, while the author is discussing the nature of Ulodendron, 

 The reasons given by Saporta, in his obituary notice of Brongniart, 

 for the abrupt cessation of the work — the immensity of the 

 scheme, the difficulties of the Tertiary floras, and the changes in 

 the author's views — do not seem altogether sufficient. Brongniart 

 lived and continued active work for more than thirty years 

 afterwards. It is, however, no part of my plan to follow the 

 later and more important development of his career. 



Saporta rightly points out tliat in his early work Brougniart 

 was the first to clearly enunciate the principle that there has been 

 a definite and gradual development of vegetation in successive 

 epochs. 



Brongniart was a great botanist, as everything he wrote proves ; 

 by far the greatest who up to that time had undertaken the 

 study of fossil plants. 



In passing from him to Bernhard Cotta, we make a marked 

 descent — Cotta was by no means great, but he did some meritorious 

 work. His book, ' Die Dendrolithen in Beziehung auf ihren 

 iiuieren Bau,' was published at Dresden in 1832, while 

 Brongniart's first volume of the ' Histoire ' was appearing. Cotta's 

 work was based on his father's collection, which included more 

 than 500 ground specimens of fossil plants. At that time such 

 specimens were sometimes ground thin, to admit of microscopic 

 investigation, but it does not appear that Cotta used the modern 

 method of mounting really thin sections on glass — that was intro- 

 duced contemporaneously in our own country by Witham and 

 Nicol. 



Young Cotta began his work as a sort of "holiday task"; 

 he appears to have been a student at the time, and modestly 

 desires that his figures may be regarded as the " Ilauptsache," 

 the text only as a necessary explanation. 



Cotta was much impressed by the evidence of a tropical climate 

 found in the rich vegetation of the Coal-measures. He adds : 

 " But not only in reference to climatic changes, but a.so with 

 respect to the gradual development of organic Nature, it is 

 interesting that we find more lowly organised plants in the older 

 than in the later rocks. Jt is possible, however, that this latter 

 circumstance ])roceeds merely from dift'erences of climate, for in 

 the Red Sandstone, for example, besides many lower plants, 

 remains of Dicotyledonous plants also frequently occur, of which 

 the numerous petrified woods with evident annual rings and 

 medullary rays alford the best proof " (p. 3). 



Cotta no doubt made too much of his favourite climatic changes, 

 but there is some force in what he says : e. <j., the difference 



