28 PLANT-LIFE ON LAND [CH. n 



evolutionary history. They are in fact "blind' 1 

 branches of the evolutionary tree. So far as any 

 relation can be traced between the Algae and 

 characteristic Land-plants this is to be sought for 

 among the simpler rather than the advanced types, 

 and even then the indications are of the slenderest. 

 But notwithstanding this, it is from the Algae that 

 we receive the clearest indications how plants at large 

 attained to many of the most fundamental features 

 that they show. The persistence of some of these 

 characters among Land-plants, even when their 

 presence is inconvenient, makes the conclusion in- 

 evitable that the origin of the vegetation of the earth 

 was ultimately aquatic. It probably sprang in the 

 first instance from free-swimming plants such as the 

 Flagellates, while the fixed Algae of our shores 

 represent an intermediate state, in which the quiescent 

 phase of self-nutrition had already become a constant, 

 as it is in them an obvious and indeed a preponderant 

 feature. 



