ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 563 



spread of the disease ; all diseased tubers should be burned, and no 

 potatoes planted on infested soil. 



Vegetable Pathology.* — P. Viala and P. Pacottet record their 

 observations on the development of black-rot of the vine. They find 

 that the fungus Guignardia Bidwellii attacks the grapes only when they 

 are green, that is, when the amount of organic acid in the fruit is 

 greater than the amount of sugar. If the fruit is protected against 

 attack until ripening has begun, by washes of copper salt, there is no 

 further risk of disease. Temperature and humidity are also important 

 factors in the spread of the disease. The fungus grows most freely in 

 a moist state of the atmosphere. It rarely develops in southern vine- 

 yards. The authors give details of these artificial cultures and the 

 effect on the fungus of varying quantities of acid. 



Cultural Experiments with " Biologic Forms " of the Erysi- 

 phacese, etc.j — E. S. Salmon has proved that within the species 

 Erysiphe graminis there are undoubted "biologic forms," both in the 

 ascigerous and conidial stages of the fungus. He has further demon- 

 strated that if the vitality of the host-plant is interfered with, its power 

 of resistance to forms to which it is naturally immune breaks down. 

 The leaves selected for experiment were superficially injured by cutting 

 any part of the epidermis or by touching the leaf with a red-hot knife. 

 On these injured surfaces were some conidia of various biologic forms 

 which would not have inoculated the normal healthy plant, and it was 

 found that they grew and produced conidiophores, which in turn served 

 to inoculate another individual of the host species — the injured plant 

 serving as a bridging species to enable the parasite to pass from one host 

 to another. The author concludes with a . summary of the various 

 experiments. 



Aschersonia.i — P. Pfennings has made a study of the fungi that 

 have been placed in this genus and of the literature dealing with it. 

 The genus has been associated with Hypoerella as a pycnidial form, but 

 the author thinks that the ascus form of Aschersonia has probably never 

 been met with. He notes that a number of similar leaf fungi are asso- 

 ciated with Coccidce. They grow on the bodies of the insects and 

 exactly imitate their appearance. The stromata thus formed are as 

 easily detachable from the leaf as are the Coccidcc. The genus Ascher- 

 sonia was established by Montague in 1848. Thirty species have been 

 described. 



Anthracnose of the Vine.§— P. Viala and P. Pacottet have culti- 

 vated the fungus causing this disease on suitable media, and have 

 obtained the conidial form with cylindrical-ovate conidia, spermogonia 

 with spermatia similar to the conidia, pycnidia, sclerotia giving rise to 

 yet another conidial form with large spores and a polymorphic mycelium, 



* Comptes Rendus, cxxxix. (1904) pp. 152-4. 

 f Phil. Trans. Roy. Soc, ser. B, cxcvii. (1904) pp. 107-22. 



% Festschr. zu Prof. Ascherson's 70 Geburtstag (1904) 4 pp. Soo also Hedwigia, 

 xliii. (1904) pp. 93-4. 



§ Comptes Eendus, cxxxix. (1904) pp. 88-90. 



