Chap, iv Taxonomy, 1 860- 1900 115 



discovery of chlorophyll in some forms rendered this 

 unsatisfactory, and they then seemed to be a class by 

 themselves, most nearly allied to the Cyanophyceae or 

 blue-green Algae. Since the early work of Cohn they have 

 attracted much attention, and when, through the labours 

 of Pasteur, the part they play in causing disease became 

 understood, the study of them led to the recognition of 

 the science of Bacteriology. This aspect, however, does 

 not come within the scope of the present volume. From 

 the standpoint of the botanist they are still regarded as 

 members of Protophyta, in accordance with the opinions of 

 Cohn and Sachs. 



In the fourth edition of the Lehrbuch Sachs gave up the 

 view that the Characeae are of sufficient importance to 

 be regarded as a class intermediate between Algae and 

 Muscineae, and relegated them to the Carposporeae. This 

 inclusion, together with that of the Coleochaeteae rendered 

 this group a not altogether natural one, and its individuality 

 was not long maintained. 



Sachs modified at the same time his original classification 

 of the Vascular Cryptogams. Fankhauser's discovery of 

 the monoecious prothallium of Lycopodium led him to 

 abandon the division into Isosporeae and Heterosporeae, 

 and to regard heterospory as a phenomenon that has 

 taken place in two distinct groups, the one a developmental 

 series beginning with the true Ferns, and the other a similar 

 series beginning with Lycopodieae. He substituted for 

 his original scheme the recognition of three main groups, 

 which he called Equisetineae, Filicineae and Dichotomeae. 

 The second of these included (1), under the name Stipulatae, 

 the Ophioglossaceae, Marattiaceae, Osmundaceae, and 

 Schizaeaceae ; (2), the Filices proper, comprising the 

 Gleicheniaceae, Hymenophyllaceae, Cyatheaceae, and Poly- 

 podiaceae, and (3), Rhizocarpeae, consisting of the Sal- 

 viniaceae and Marsiliaceae. The Dichotomeae, so called 



H 2 



