26 Transaciions British Mycological Society. 



11.— The host plant derives the greater advantage as in 

 Gastrodia data. 



Ill, — The fungus evidenilv gains most as in many of the 

 series of endophytic mycorrhizas. 



Fungi have been demonstrated once and gain as somewhat 

 harmless inhabitants of the thallus of hepatics : they may 

 interfere with the metabolism of individual cells but they do 

 not seem to produce any effect on the general life of these 

 plants. A benet^cial symbiosis with mosses has however 

 been established by Servettaz.* He made a series of 

 cultures of mosses on artificial media, and, in the cultures 

 of Phasciim cuspidatum, he found present a fungus of the 

 Oospora tvpe which reacted in an extraordinary way on the 

 development of the moss. wSo important was the presence 

 of the fungus, that without it the moss did not advance 

 be\'ond the protonema stage, while in control cultures 

 which were associated with the fungus, the stem had, during 

 a similar period, reached full growth. vServettaz ascribes 

 the advantage as due to gases produced by the fungus along 

 with acid products formed by it from the glucose of the 

 nutritive medium. 



Lichen symbiosis. The most complete case of a living 

 association between fungi and green plants is to be found 

 in the large and varied class of lichen plants in which is 

 represented a successful instance of mutual give and take 

 between the two components, algae and fungi. Lichens as 

 a well marked and recognizable group of plants have been 

 known and classified from the early days of botanical study 

 side by side with other divisions of the vegetable kingdom, 

 though their exact relation to other groups was long a puzzle 

 to systematists. Many workers had recognized the extraordin- 

 ary likeness of the lichen plant to algae on the one hand and 

 to fungi on the other, but it was Schwendener who about 

 sixty years ago had the courage to announce the dual hypo- 

 thesis, that two different organisms were combined in the 

 lichen thallus. This theory, much combated at first, has 

 been graduall}- accepted bv lichenologists, and the 

 controversies which never cease to rage round lichens, now 

 centre on the relation between the two svmbionts, the alga 

 and the fungus. It is here also a question of nutrition, and 

 of the mutual adaptation of the two associated plants to their 

 composite existence. 



It has been strongly held by some that the association 

 is one of parasitism or semi-parasitism and that the fungus 



* Servettaz, '13. ' 



