Pflanzenkrankheiten. 49 



cacaoicola Hennings. The fungus kills the trees when they have 

 become leafless by some other cause, and also causes the "brown- 

 rot' of the pods. Healthy trces and pods however are never affected, 

 so that the fungus may be called a wound-parasite. 



The author, who cultivated the Diploäia under different circum- 

 stances, tbund that sometimes there appeared pycnidia, belonging 

 to the genus Diplodia, sometimes pycnidia of Chaetodiplodia and 

 sometimes of Lasiodiplodia. She concluded that the characteristics 

 of these three genera are due to outward circumstances, that Chae- 

 todiplodia and Lasiodiplodia must be annulled and the genus Diplodia 

 maintained. 



The combative measures of this disease should consist in keeping 

 the cacoa trees in good condition, specially combating Thrips, 

 which favours the spread of the disease and by pruning and thin- 

 ning in the right season. Westerdijk. 



Kruyff, E. de, Het Wortelrot der Cassave. (Teysmannia. XXL 



p. 147. 1910.) 



Verf. beobachtete eine Fäule der Wurzelknollen an der Cas- 

 save {Manihot utilissi^nä). Es gelang ihm eine Bakterie aus den 

 kranken Teilen zu isolieren: Infektionsversuche hatten aber keinen 

 Erfolg. Eine eigentümliche Erscheinung dieser Krankheit ist fol- 

 gende: Neben der kranken Knollen kommen an derselben Pflanze 

 immer gesunde vor, welche durchaus gesund bleiben. 



Westerdijk. 



Massee, G., Diseases of cultivated plants and trees. (Lon- 

 don. Duckworth & Co., 1910. Crown 8vo. 602 pp., 171 figs. 



7s. 6d. net.) 



The present work is on similar lines to the „Textbook of Plant 

 Diseases" published by the author in 1899, but enlarged and brought 

 up to date. In addition to diseases caused.by fungi, the new work 

 contains chapters on plant maladies caused by mites and eelworms. 

 and also notes on injuries due to frost, hail and smoke, it thus 

 Covers a considerably wider field than the „Text-Book". 



In addition to the diseases found in Britain, many of the more 

 important tropical diseases are dealt with, and also those occurring 

 in the United States. The Book is not suitable for a detailed 

 abstract; it will suffice to say that it is the most complete compen- 

 dium of its kind in existence, and that scattered through it much 

 useful Information and advice is published for the first time. 



^ A. D. Cotton (Kew). 



Münch, E., Versuche über Baumkrankheiten. (Naturw 

 Jahrb. Land- und Forstwirtschaft. VIII. p. 389—408. und 425- 447. 

 mit 18 Fig. 1910.) 



Der Verf. hat in einer früheren, in dieser Zeitschrift gleichfalls 

 besprochenen, Arbeit gezeigt hauptsächlich auf Grund von Labora- 

 toriumsversuchen) dass das Zustandekommen einer Pilzerkrankung 

 im Holz und in der Rinde eines Baumes von zwei Faktoren ab- 

 hängt: nämlich herabgesetztem Wassergehalt und Anreicherung an 

 Luft (namentlich an Sauerstoff) im befallenen Gewebe. 



Die vorliegende Arbeit bildet zu jener früheren eine Ergänzung, 

 insofern als die damals gewonnenen Ansichten an im Freien wach- 

 senden Bäumen auf ihre Allgemeingiltigkeit geprüft werden. 



Botan. Ceatralblatt. Band 116. 1911. 4 



