438 SUMMARY OF CURRENT RESEARCHES RELATING TO 



potato-field caused by Rhizoctonia violacea. He states that the fungus 

 cannot develop except in presence of an acid, and flourishes best in sour 

 badly drained and poorly aerated soils. So he recommends liming of 

 the ground and the avoidance of acid manures. 



M. G. Fron * has studied the straw blight of cereals, which has been 

 attributed to Ophiobolns graminis and Leptosphxria herpotrichoides . The 

 author ascertained that the trouble was mainly due to the latter fungus. 

 The disease appears in May and the beginning of June, and the affected 

 portions of the grass assume a grey colour and wither. The perithecia 

 of the fungus ripen in November and December. A summer form of 

 the fruit is probably a species of Cercosporella. The fungus only 

 develops in the presence of an alkali. Its growth is arrested in an acid 

 medium. 



A. Lendnerf has studied a disease of tulips caused by a Sclerotinia 

 tidiparvm. He finds that not only the end bud, but also the enveloping 

 scales are attacked. The difference between the attack of this fungus 

 and that of Botrytis parsitica is described. Diseased plants sent from 

 Holland spread the disease in Geneva. 



Study of Mycorhiza.t — Josef Fuchs made a long series of cultures 

 of pine trees in sterilized soil, pure cultures of fungi from various families 

 as well as of the Mycorhiza fungus. Most of the cultures were unsuc- 

 cessful. He concludes that the Mycorhiza fungus has its origin in the 

 seed itself, and that it does not grow outside the roots. Important and 

 interesting biological results are given. 



Lichens. 



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



Study of Symbi08is.§ — 0. Treboux has repeated work done by Urtari 

 and by Beijerinck on the physiology of lichen gonidia, more particularly 

 of Gystococcus humicola. He enters somewhat elaborately into the deter- 

 mination of the alga, and gives the results of his experiments. He denies 

 that Gystococcus as gonidium is a peptone-alga : he found that other 

 nitrogen compounds served equally well as food supply, and he found 

 that "the alga in the lichen and as a free-hving organism were exactly 

 alike. He also considers that the alga suffers considerably from its 

 imprisonment within the lichen thallus. It grows slowly, increases very 

 little, and loses its healthy green colour. 



Oropogon loxensis.H— R. Heber Howe gives a microscopic descrip- 

 tion of the thallus and spores of this lichen which he had at one time 

 included in the genus AUctoria. It has a cgespitose prostrate thallus of 

 slender shining brown or black branches. The spores are solitary in the 

 ascus, muriform and brown. It is a subtropical plant. 



* Ann. Sci. Agron.-franc. etrang., xxix. (1912) pp. 3-29 (5 pis.). See also Bull. 

 Bur. Agric. Intell. PL Dis., iii. (1912) pp. 1054-6. , -u . r, . ,w 



t Bull. Soc. Bot. Geneve, s6r. 2, iii. (1911) pp. 126-31. See also Bot. Centralbl. 

 cxix. (1912) p. 471. ^ ^ 



X Bibliotheca Botanica. Stuttgart (1911) Ixxvi. 82 pp. (4 pis.). 



§ Ber. Deutsch. Bot. Gesell., xxx. (1912) pp. 69-80. 



II Mycologia, iv. (1912) pp. 152-6 (1 pi.). 



