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 diploid 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. 
