CHAP, in The Study of the Cryptogams 233 



1875, and Leclerc du Sablon, who investigated especially 

 Aneura in 1885. The formation of the curious air chambers 

 of the Marchantiaceae was first explained by Leitgeb in 

 the course of his work, the paper appearing in 1880. 

 Naegeli, in the A bstammungslehre, gave an account of the 

 mode of origin of foliar members in the whole group of 

 the Bryophyta. Remarkable work on the cytology of the 

 Liverworts was done by Farmer in 1894 and 1895. He 

 investigated the phenomena attending nuclear division in 

 several species and discovered the existence of centrospheres 

 and the part they play in the karyokinetic changes. 



Leitgeb contributed also to our knowledge of the Mosses. 

 His paper on Sphagnum appeared in 1868, and he returned 

 to the study of the group after he had completed his 

 researches on the Liverworts. 



Pringsheim and Stahl both conducted investigations on 

 the Mosses in 1876, studying especially the protonema and 

 its relation to the moss plant. Kienitz-Gerloff worked out 

 the development of the sporogonium in 1878. Other 

 researches were conducted by Russow (1887), Waldner 

 (1887), and Vaizey (1887-90). The researches of the latter, 

 though partly anatomical, dealt with the physiological 

 problems presented by the group. 



We have already noticed how great an impetus to the 

 study of the Vascular Cryptogams or Pteridophyta was 

 given by the work of Hofmeister. During the years that 

 elapsed between the appearance of his great treatise and 

 the close of the century this subject seemed to fascinate 

 investigators more than any other, and innumerable papers 

 appeared elucidating certain points he had left unsolved, 

 or adding to our knowledge of structure and life-history. 

 The gradually increasing mass of detailed information gave 

 rise to speculation and controversy upon affinities and 

 relationships, which are reflected in the taxonomic writings 

 of the time. As years passed and the records of the rocks 



