02() Fungi. — Bacteria. 



mettent de conclure qu'en somme il n'y a pas de difference 

 essentielle entre les plantes uni-et pluri-cellulaires dans la facon 

 de se comporter vis-ä-vis de ces irritations exterieures. 



Mathilde Goldiluss. 



Ward, H. Marshall, On the relations between the Host 

 and Parasite in the Bromes and the ir Brown Rust. 

 Puccuiia dispersa. (Annais of Botanv. XVI. June 1902. 

 p. 233—315.) 



Prof. Ward's extended work on this subjeet, eoncerns; 

 the characters and behaviour of the „seed" and the seedlings 

 of the species of Bromus examined, together with observations 

 on the leaves of young plants, and the systematic relationships 

 of these species: the description of methods of eulture by which 

 these grasses can be grown and kept growing absolutely free 

 from danger of accidental infection by rust fungi: the means 

 by which pure eultures of the Uredo in question can be trans- 

 ferred to such pure eultures of the Bromes, and the comparison 

 of infected and non-infected plants compared; and lastly, the 

 behaviour of the Uredo itself on, and in, the different species. 



After a detailed aecount of the species of Bromus used in 

 the experiments, the author passes on to infection. Three 

 phases are distinguished 1) the germination of the uredospore, 

 2) the act of inoculation and infection, and 3) the ineubation 

 period or growth of the mycelium in the tissues. Temperature 

 is perhaps the most important factor which eoncerns the germi- 

 nation of the spore; the best germinating temperature being at 

 or near 20" C, and the maximum not far from 26° or 27° C. 

 and the minimum 10 — 12° C. The spores were found to ger- 

 minate successfully after being frozen for a period of 10 minutes, 

 but unsuccessfully if frozen for 4 or 5 hours or if heated to a 

 temperature above 30° C. Spores germinate readily in the dark 

 as well as in the light. 



The methods of infection and the results of infection are 

 described; followed by an aecount, containing numerous tables, 

 of a large series of experiments condueted with various species 

 of Bromus. 



From the results of these experiments, together with an 

 exhaustive comparative examination of the structural peculiarity 

 of the host plants, the conclusion is drawn that it is „very pro- 

 bable that by gr adual Variation and adaptation, the fungus 

 can pass to all or nearly all the species of Bromes in turn, 

 even to such as have hitherto appeared immune. That by 

 gradual passage from variety to variety, and from one species 

 to a closely allied one, such spores may be gradually adapted 

 to different hosts in nature, seems an obvious corollary from 

 the facts", and further „that the resistance to infection of the 

 „immune" or „partially immune" species and varieties is not to 

 be referred to observable anatomical or structural peculiarities, 

 but to internal, c. e. intraprotoplasmic, properties beyond the 



