BEITISH MOSSES. 65 



spores. The spectacle of an opening orspangium of a 

 Jungermannia is a very interesting one. 



It is remarkable that in the true Mosses, with their 

 much more highly organized capsules and spore cases, 

 these elaters have disappeared. 



If the patience of my reader hold out, I will ask him, 

 for the last time, to refer back to my table A, where he 

 will find that last of all in the series come the Marchantiacse, 

 so named from the best known species of the group, the 

 Marchantia polymorpha, a plant so remarkable and so 

 worthy of full consideration, that I fear that if I embarked 

 on it I should weary my reader beyond endurance, so I 

 leave it, at least for the present. 



Distribution in Time. It will be interesting now to 

 enquire how long the present Moss flora of England has 

 existed. How far back can we carry our knowledge 

 of the existence on the world's surface of these 

 delicate organisms ? It is evident that they have 

 had but a small chance of leaving evidence of their 

 existence as fossil remains, because whilst the strong, 

 almost wiry, vessels of the ferns have a great power of 

 resisting decay and so gettingpreserved, the delicate cellular 

 structure of the Mosses offers little or no resistance 

 to that process. Hence it is that the fossil remains 

 of Mosses are not very numerous, or for the most 

 part very ancient. Yet we have some materials to answer 

 the enquiry. Three ancient collections of Mosses enable 

 us to throw some light upon it. In an interglacial bed 

 near Crofthead, in Kenfrewshire, eleven species of Moss 

 were discovered, and with one possible exception all are 



E 



