334 SUMMARY OF CURRENT RESEARCHES RELATING TO 



In 1015 Rayner published an account of the obligate symbiosis of 

 Calluna vulgaris with a fungus ; she isolated it, grew it in pure culture, 

 and found that a fruiting body was formed with some resemblance to a 

 Phoma. Calluna itself in pure cultures does not develop beyond the 

 seed-leaf stage, and is incapable of forming roots. In this plant the 

 fungus extends through the whole of the plant in an extremely attenuated 

 condition right to the ovaries, so that the seeds are infected with the 

 fungus in the form of delicate hyphse on the surface of the seed-coat. 



Gallaud's views on the physiology of the relationship between the 

 two organisms is discussed at some length, more especially the physio- 

 logical relationships between the two plants. The work of Kusano on 

 Gastrodia elata is also dealt with at length. The writer has adopted 

 Bernard's view of the relationship, viz. "that the phenomenon of 

 mycorrhiza in plants is only an expression of the warfare waged continually 

 by all organisms against parasitic invasion of their tissues. The flowering 

 plant possessing mycorrhiza has done more than hold the invader ia 

 check ; it has turned the intrusion to its own advantage." 



Lichens. 



(By A. LoEBAiN Smith, F.L.S.) 



Edible Lichens.* — An instance of the use of lichens as food has; 

 been recorded from America by Tom Wilson. The Indians in British 

 Columbia collect Alectoria jubata, which they prepare by placing in a 

 heated pit alternate layers of damp grass and of lichens till the pit is 

 full. Hot stones are "laid around, and for a day or more the whole 

 mass is kept as hot as possible ; it is then ready for consumption. If 

 not well prepared it is apt to mildew, but after a month it was found to- 

 be quite good for eating. 



New Rare or Critical Lichens.t— W. Watson draws attention to the 

 renewed interest in lichens on account of their dyeing properties. He 

 describes two new species of Pyrenocarpei, Thelidium tetrestre, which 

 grew on the soil of a hedge-bank in South Somerset, and PoJyhlastia 

 mortensis, collected on the soil-cap of walls or on mortar, often on 

 decaying mosses, at Morte, North Devon, near the sea. Diagnoses are 

 given, and the characters that differentiate these from related species 

 are noted. A list of somewhat rare lichens with critical notes \b 

 appended. 



* Ottawa Naturalist, xxi. (1916) pp. 17-21, See also Bryologist, xx. (1917) p. 32, 

 t Journ. Bot., Iv. (1917) pp. 107-11 (figs.). 



