668 Pfianzenkrankheiten. 



basis. There is certainly a very great pressure exerted to cause the 

 exudation of so much slime on the surface of twigs. The cortical 

 cells of the bark are very close together and some force must be 

 exerted to cause them to tear appart. It may be that the osmotic 

 pressure of the substance in which the bacteria are found is sufli- 

 ciently great to rupture the cell walls. Evidence of such pressure 

 is found in the large cavities which are formed in the xylem, cortex 

 or pith. These cavities are frequently rounded or oval and suggest 

 an equal pressure in all directions. The result of a process of en- 

 zymic Solution should be the gradual dissolution of the entire wall 

 and not merely a tear at one place. There probably is such digestion 

 of the walls to some extent but osmotic pressure is, in the writers 

 judgment, a more important factor in their final rupture. 



M. J. Sirks (HaarlemX 



Gregory, C. T., A rot of grapes caused by Cryptosporella viti- 

 cola. (Phytopathology. III. p. 20-23. 1913.) 



The writers conclusions are: 



The berries are attacked shortly before, and at maturity, by 

 the same fungus that causes the dead-arm disease of the grape vine, 

 producing a rot which in all its stages of development is very 

 similar to black rot. On close examination the two can be distin- 

 guished, but the most apparent difference is that this fungus attacks 

 the grapes only when nearly ripe, while the black rot ceases to 

 spread extensively in New York vineyards after the first of August. 



Cultural characteristics, the characters of stained sections, the 

 presence of scolecospores, the sucessful inoculations in the stem 

 which produce typical necrotic lesions, together with the reisolaüon 

 of the same fungus from artificalh'- infected tissue, all combine to 

 show that this disease is produced by Cryptosporella viticola. 



" M. J. Sirks (Haarlem). 



Jamieson, C. O. and H. W. Wollen weber. An external dry- 

 rot of potato tubers caused by Fusarium trichothecioides , 

 Wollen w. (Journ. Wash. Acad. Sc. II. p. 146—152. 1912.j 



In Order to prove the parasitic nature of Fusarium trichothe- 

 cioides WoUenw., inoculation experiments have been carried on under 

 controUed conditions in our greenhouses during the past two sea- 

 sons. Potato plants, grown in sterilized soil, from selected and dis- 

 infected seed were used, and pure cultures of F. trichothecioides 

 inoculated into the stem just above the surface of the ground. In 

 twelve days a wilting of the foliage was noticed accompanied by a 

 yellowing of the leaves and a discoloration of the tissue about the 

 inoculation pricks. In three weeks time the fungus infection had 

 produced effect upon the plants, shown in the wilted condition of 

 the foliage, in the constriction of the stem at point of inoculation. 

 Upon the surface of the discolored area could be seen a growth of 

 of powdery slightly pinkish m5'^celium and spores. Microscopic exa 

 mination and isolation showed this fungus to be F. trichothecioides. 

 Pure cultures of this same Fusarium were laier obtained from 

 tubers produced upon a plant diseased through inoculation. 



From results of other experiments it is clear that conditions of 

 temperature, and moistare undoubtedly pla}?^ an important part in 

 the beginning and in the progress of infection, and a better under- 

 standing of these conditions may prove of great value in attempting 



