454 The Living Plant 



times as many as of Algae), while there doubtless remain a great 

 number still to be discovered. 



We turn now to consider the place of the Fungi in our tree of 

 descent (figure 177). It seems perfectly clear that they all are 

 derived, either immediately or remotely, from the Algae. We can 

 imagine that as the Algae became large and abundant, some kinds 

 took to growing upon others, at first merely as a convenient situa- 

 tion, but later making use of the decaying remains. But in 

 nature, as in human affairs, it is only the first step which counts, 

 and the transitions from a dead to a dying, then to a sickly, and fi- 

 nally to a healthy host are easy, giving origin in turn to an epi- 

 phytic, saprophytic and, finally, parasitic mode of life. Then, as 

 the Green Algae evolved into the higher and air-living forms and 

 came out to live on the land, they were accompanied by these par- 

 asitic Algae, which gradually became more and more altered in 

 adaptation to the new conditions of their existence. And there 

 you have the Fungi, which are nothing but parasitic Algae, al- 

 though in some cases with an ancestry so ancient that we can 

 hardly trace a sign of their primitive origin. The various principal 

 sub-groups of the Fungi, the Basidia division to which the Mush- 

 rooms belong, most ancient and specialized of them all, the Sac 

 Fungi, which include the Lichens, the Algoid Fungi, which com- 

 prise the water forms and others that are most like the Algae, are 

 shown in our tree in conjunction with their most probable an- 

 cestral branches of the Algae. 



The Moss-plants, or Bryophytes. These are typically the carpet 

 plants of the land, especially the woods, where they form the 

 fine close covering over ground, boulders, and prostrate tree- 

 trunks; but they also extend out beyond into places that are open, 

 particularly where wet. They comprise two well-marked divi- 

 sions. First are the Liverworts, which mostly lie flat on the 

 ground outspread in small thin fronds suggestive strongly of some 

 kinds of Algae, though others bear delicate leaves. Second are 

 'the true Mosses, much more familiar, which have upright, slender, 



