chap, hi The Study of the Cryptogams 235 



indeed over a very large part of the field, but dwelling 

 more particularly on the Ferns, was the research conducted 

 by Poirault, which was published in 1893. This was from 

 the laboratory of Van Tieghem, and was carried out partly 

 under his influence. It dealt especially with the anatomy 

 of the vegetative parts, and the structure of the elements 

 of the tissues, throughout the group. 



Another book of the period was Douglas Campbell's 

 Mosses and Ferns, published in America in 1895. It 

 embraced the results of a large number of investigations 

 into the anatomy of both groups carried out during many 

 many years by himself. 



Of all the mass of literature on the different sub-groups 

 of the Pteridophyta, it is only possible here to mention 

 some of the more important memoirs. Naturally, research 

 on the Ferns should receive the first attention. 



The last addition to the group of the Ophioglossaceae, 

 Helminthostachys, was first described by Prantl in 1883, 

 when he dealt especially with the fertile spike. An inves- 

 tigation of the sporangia was made by Bower in the course 

 of the ' Studies ', and its results appeared in 1896. The 

 vegetative structure of the plant was described by Farmer 

 and Freeman in 1899. 



The anatomy of Ophioglossum was worked out by 

 Russow in 1872 and by Holle in 1875, and symbiosis of 

 its roots with a fungus was demonstrated by both observers. 

 Holle studied the development of the tissues of the whole 

 plant from the apical cell. Further contributions to the 

 same subject were made by Van Tieghem in the Traite de 

 Botanique, by Prantl in 1883, Poirault in 1892, and Ros- 

 towzew in the same year. 



The prothallia of several members of this group were 

 discovered and examined. Before i860 Hofmeister had 

 investigated that of Botrychium virginianum, but his 

 material only supplied the older stages of its development. 



