232 The Anatomy of Plants 



the dissemination of the latter over the surface of the 

 thallus by means of water. Further, he said that the 

 contents of a spermatium pass into a trichogyne when the 

 two come into contact, fusion of their respective walls soon 

 taking place. Stahl thus brought the fertilization of the 

 lichens into line with the same process in the Rhodophyceae. 



The improvement of methods led to more minute investi- 

 gation of the cytology of the Ascomycetes and the Uredineae 

 during the later years of the century. The researches, quite 

 at its close, of Dangeard in France and of V. H. Blackman 

 in England threw a good deal of light upon the nature 

 of the sexual processes, and the fusion of nuclei of various 

 origins, bringing into question the views of the older writers 

 upon the sexuality of the members of the group, and at 

 any rate suggesting that the problem is of a much more 

 complicated character than had been supposed. The 

 question was left at a very interesting stage when the 

 century closed. 



The work of Brefeld included a very careful study of 

 the biology of many of the fungi and the nature of their 

 dependence upon external conditions, together with the 

 effect of the latter upon their pleomorphy and their repro- 

 ductive processes. This work appeared in 1881. Klebs's 

 treatise of 1896, though mainly concerned with the Algae, 

 extended Brefeld's researches on their fungal relatives. 



The work on the Bryophyta between 1860 and 1900 

 included the exhaustive researches of Leitgeb on the 

 Liverworts. These appeared at intervals between 1874 

 and 1882, and formed together a masterly exposition 

 of their structure and development. Leitgeb showed him- 

 self to be the greatest specialist on the minute structure 

 of the Hepaticae. Other workers on the same group were 

 Strasburger, who investigated Marchantia in 1868, Kienitz- 

 Gerloff, 1874-5, Fellner, who studied the germination of 

 the spores of Riccia and the structure of its thallus in 



