78 ALTERNATION IN THE THALLOPHYTES 



the greater interest to trace such internal evidence as there is of the method 

 and manner of the intercalation of the dipioid phase in the life-history of the 

 Archegoniatae : and an important question will be what circumstances they 

 probably were which conduced to fixing permanently the alternation that 

 resulted, and to making it so constant a feature as it has been in the 

 upward development of the green plants of the Land. This will form 

 the subject of the next chapter. 



