Algae. — Eumycetes. — Pflanzenkrankheiten. 295 



der Gattungen werden mitgeteilt: Enter oniorpha, Cladophora, Con- 

 tarinia, Cruoriella, Peyssonellia, Phyllophora. 



Die Zusammengehörigkeit von Rhodochorton membranaceum 

 Hauck. (non Magnus) und Chantransia niinutissima Hauck wird 

 bewiesen. Verf. nennt die Art Rhodochorton Hauckii. Die syste- 

 matische Stellung von Chondria tenuissUna und Alsidiuni Helmin- 

 thochortos wird geklärt, von letzterer Pflanze werden die Anthe- 

 ridien beschrieben. 



Als neue Arten werden aufgestellt: 



Enteromorpha pallescens, Afitithatnnion SpyrograpJiidis, A. te- 

 nuissimtnn, Hymenocloniuni adriaticimt und Elachista Kuckuckiana. 

 Von interessanteren neuen Formen bereits bekannter Arten werden 

 aufgeführt: TJlva Lactuca f. rosidans, Chaetomorpha linum f, 

 hrachyarthra, Lithophylhim tortuosiirn f. subplana. Als neu für 

 das Mittelmeergebiet wird Pringsheimia scutata nachgewiesen. 



In einem besonderen Teil „Beiträge zur Kenntnis der marinen 

 Sommer- Vegetation von Triest und Rovigno" sind die oekolo- 

 ^ischen Studien zusammengefasst. W. Herter (Berlin Steglitz). 



Hawkins, Lon A., Growth of parasitic fungi in concen- 

 trated Solutions. (Journ. Agric. Research. VII. p. 255—260. 

 1916.) 



It is apparent that plant parasites must quite commonly possess 

 the ability to withdraw water from more or less highly concentrated 

 Solutions and to grow in them. The relative concentration of the 

 cell sap of parasite and host has been studied in the caseof phane- 

 rogamic parasites by Mac Dougal and Ca n non and by Senn 

 who deraonstrated that the osmotic pressure of the parasite is 

 higher than that of the host. It seems probable that fungus para- 

 sites should be able to live and grow in Solutions of a considerably 

 higher concentration than the total concentration of their host 

 plants. To obtain more evidence on this point the author set up a 

 series of experiments with ten common parasitic fungi, which were 

 grown in Solutions of salts and sugars of rather high concentrations. 

 Following two different methods for the demonstration of the high- 

 est concentrations of the various substances used in which the 

 fungi could grow, it was found that in every case the fungi grew 

 readily in Solutions in which the diffusion tensions were much 

 higher than the total diffusion tensions of the dissolved substances 

 in the Juices of their host plants. Whether this ability is due to 

 the osmotic pressure in the fungus being originally higher or to 

 other still unknown factors is a question which needs further in- 

 vestigation. Van der Lek (Bennekom). 



Allard, H. A., Further studies ofthe mosaic disease of 

 tobacco. (Journ. Agric. Research. X. p. 651—631. 1917.) 



The author's own summary runs as follows: 



1. The virus of the mosaic disease of tobacco is present in the 

 trichomes of the leaves, as well as in the tissues of the lamina. 

 The disease may be communicated to healthy plants by inoculating 

 the virus in the trichomes alone. 



2. The virus does not readily invade uninjured trichomes or 

 leaf tissues when merely sprayed upon the plants. Infection readily 



