n8 Morphology BOOKI 



separating the Myxomycetes from the rest ; a third division 

 the Embryophyta Zoidiogama, or Archegoniatae 

 included Eichler's Bryophyta and Pteridophyta, and a 

 fourth .the Embryophyta Siphonogama comprised the 

 Phanerogams, which he arranged in two subdivisions, each 

 co-ordinate with Bryophyta and Pteridophyta viz. the 

 Gymnospermae and the Angiospermae. 



Though Engler's system was adopted largely on the 

 continent of Europe, it did not at first obtain acceptance 

 in England, where Eichler's main divisions were adhered 

 to up to the end of the century. 



The acceptance of these four main groups and the 

 discussion of their relationship to each other directed 

 inquiry into the question of phylogeny, which gradually 

 assumed a great importance in the literature of the period, 

 and maintained its interest throughout the closing years of 

 the century. The inquiry received considerable support 

 from the renewed activity that was displayed in the in- 

 vestigation of the fossil remains of plants from the different 

 geological strata, interest perhaps being greatest in the 

 question of the origin of the Phanerogamic Flora. To 

 this branch of study reference will be made in a later 

 chapter. 



The difficulty of tracing the descent of the Bryophyta 

 from the Algae was recognized by all. As we have seen, 

 it assumed great prominence in connexion with the dis- 

 cussion of the homologous and antithetic theories of altern- 

 ation of generations, and while no writer claimed to have 

 solved the problem, there was a general agreement that 

 the explanation must be looked for in connexion with 

 the migration of plants from an aquatic to a terrestrial 

 environment, and the consequent upsetting of their physio- 

 logical equilibrium. That it was due to some far reaching 

 cause was obvious, when the course of evolution in the 

 group of the Algae was studied and compared with that 



