io6 FLOWERLESS PLANTS 



we still speak of the lichens as species, they 

 are only so in so far as they conform to a cer- 

 tain manner of growth which makes such an 

 identification possible. Far from being one 

 individual, every patch of lichen is composed 

 of many thousands of entities, some of which 

 could, and indeed often do, lead a separate 

 existence. It is now some years since the 

 idea of the dual composition of lichens was first 

 of all mooted, when De Bary suggested that 

 many of these plants bore striking resem- 

 blance to fungi on the one hand and algas on 

 the other. The idea was taken up by certain 

 patient observers, who set themselves the task 

 of finding out the truth of the matter. This 

 work was carried out in the face of an enormous 

 amount of opposition from those who had 

 made lichens their special study. Finally, it 

 was established beyond a shadow of a doubt 

 that all these plants are not simple growths 

 at all ; rather are they to be regarded as 

 colonies formed of thousands of individuals, 

 with, however, one predominant partner. The 

 principal in the alHance is a fungus which, as 

 in a network, encloses large numbers of small 

 green algae. It is this dual arrangement which 



