ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 65 



showed any power of assimilating free nitrogen when grown in nitrogen- 

 free media. M yceliophora and Fusarium show no such power even in 

 nitrogen-containing media. Other results of more or less interest are 

 also recorded by the writer. 



Tuberization in Spiranthes autumnalis.* — C. Beau records a series 

 of observations on the connexion between mycelial infection and the 

 formation of tubers in this orchid. The adult plant possesses two to live 

 large tuberized roots surmounted bv the floral axis and bearing a lateral 

 rosette. The cortex of the root is invaded by the endophytic mycelium. 

 From their older roots arise tubercles at the end of the flowering season 

 which eventully grow into the new roots and are also occupied by the 

 endophyte, though only when development is complete. If they are 

 separated from the parent plant before this stage they are (and remain), 

 fungus-free. Beau thus proved that tuberization was not an effect of 

 mycelial invasion. Different results were obtained by growing the 

 orchid from the seed. Germination of the seed is normally dependent 

 on the presence of the fungus. 



Plant Diseases. — C. 0. Farquharsonf has recorded various diseases 

 observed by him in Southern Nigeria. Two rubber diseases (on the 

 roots of Hevea brasiliensis) have been traced to the fungi Fomes semi- 

 tostus and Hymenochsete noxia. A stem disease which arises generally 

 at the forks was caused by Corticium salmonicolor. It frequently kills 

 the whole crown of the tree. The two former fungi were also found on 

 the roots of cacao-trees. Canker of cacao and pod diseases were also 

 noted. 



Cotton was found to be peculiarly liable to physiological diseases, 

 such as discoloration of the leaves, the specific causes being imperfectly 

 known ; the leaves are attacked by several fungi. 



J. J. Taubenhaus and T. F. Manns $ have published an account of 

 the diseases to which the sweet-pea (Lathyrus odorata) is liable in the 

 United States. Mosaic disease is frequent.; the cause of the leaf-spotting 

 is unknown, but it is infectious, and can be induced by inoculation. 

 The roots are attacked by Thielavia basicola and by Rhizoctonia vagans. 

 Stem or collar rot is caused by Sclerotinia liberliana, which attacks the 

 seedlings at all stages and quickly causes rotting of the tips, with sub- 

 sequent collapse of the plant. Species of Fusarium also cause diseases 

 of roots and stems ; leaves are destroyed by Qlomerella rufo-maculans 

 and by powdery mildew, which in this country has been identified as 

 Erysiphe Polyyoni. 



H. Miiller-Thurgau § gives the final paper on a disease of vine- 

 leaves caused by Pseudopeziza tracheiphila, which in some districts has 

 done great damage. The author describes the development of the fungus 

 from the spore, having obtained cultures on dead leaves. He discusses 



* Comptes Rendus, clviii. (1913) pp. 512-15. 



t Ann. Rep. Agric. Dept., 1912, pp. 6-9. See also Bull. Agric. Intell. Rome, 

 iv. (1913) pp. 1454-5. 



X Dept. PI. Path. Delaware Coll. Exper. Stat. See also Bull. Agric. Intell. 

 Rome, iv. (1913) pp. 1455-7. 



§ Centralbl. Bakt., xxxviii. (1913) pp. 586-621 (1 pi.). 



Feb. 18th, 1914 F 



