20 BEITISH MOSSES. 



The appearance of similar organs in two independent 

 lines of development i.e. of the leaves, stem, and 

 epidermis in the Mosses, and then in the ferns, without 

 any relation of descent, is a thing well worthy of being 

 pondered over by those who study evolution : it may 

 suggest that the two lines of development, though inde- 

 pendent, are governed by some common principle which 

 brings about such like results : it may be compared with 

 the parallelism of the stages of evolution which are reached 

 independently by the placental and marsupial mammals. 



Such are some of the reflections and conclusions which 

 follow from the adoption of that doctrine, current amongst 

 botanists, of the presence of two alternative generations in 

 what appears at first sight to be the history of a single 

 generation. It would be presumptuous in one who makes 

 no claim to any other position than that of a learner to 

 assail the conclusions of great authorities ; but it may be 

 allowable to observe that I have sometimes asked myself 

 whether the theory can stand the strain of all the conclu- 

 sions which arise from it ; that at any rate these conclu- 

 sions are such as to seem to demand that the foundations 

 of the theory should be very firmly laid in indubitable 

 facts ; that the approach of some ferns, especially the 

 filmy ferns, to the Mosses is, on the theory we have been 

 adopting, merely phenomenal and delusive ; that the 

 facts we are about to consider show that Nature can 

 suppress one whole so-called generation without imperil- 

 ling the life of the organism, and that the facts known as 

 apospony and apogony produce the same results in the 

 case of ferns. Perhaps in future years, and with fuller 



