508 proceedings: the botanical society 



pecially in street planting, suffered most from drouth, the margins of 

 leaves being killed; in the worst cases whole leaves except parts imme- 

 diately adjoining the veins died. Most other trees, including Acer ru- 

 hrum, escaped serious leaf injury. A northeast storm with hail and a 

 66-mile wind at the end of July injured many species, especially sugar 

 maple and American basswood. The storm injury to maple resulted in 

 the death of part of the leaf at the -margin and between the veins, with- 

 out laceration or other external indication of mechanical injury. These 

 storm-injured maple-leaves could be distinguished from those hurt by 

 drouth only by their limitation to parts of trees especially exposed to 

 the storm. 



Pitfalls in 'plant 'pathology. Dr. H. W. Wollenweber. A revision 

 of the hundreds of species of Fusarium in literature has led the speaker 

 to believe that the genus Fusarium contains only 30 to 50 different 

 forms. A sharp criticism was given to mycologists who send unre- 

 liable specimens to the international " Pilzcentrale" in Amsterdam. 

 Many errors are caused by the earlier opinion that Fusaria as a rule 

 are adapted to one particular host. Upon receiving a request for a 

 particular wound-parasitic Fusarium even the author of that species 

 is liable to make the following mistake. He isolates from a diseased 

 specimen a fungus, which he sends to the inquirer when it has produced 

 sickle shaped spores which he thinks belong to species* previously de- 

 scribed by him. Upon a second request perhaps a year later he would 

 isolate similarly from another specimen of the same host presuming to 

 obtain the same fungus. The speaker by chance checked up the strains 

 sent under the same name to three different places at various time by 

 the same author and found two different species. Careful reference to 

 the source and the method of isolations and determination are required 

 to eliminate mistakes of this sort. 



If one is unfamiliar with the method used to develop sporodochia 

 with normal spores he might consider a subnormal spore as normal. 

 This leads to another pitfall, where diagnoses of the same species disagree 

 and the subnormal fungus is described as new. An example of this 

 kind is F. trichothecioides Wr., wound parasite of the potato, a fungus 

 the early stage of which is described as F. tuherivorum by Wilcox and 

 Link. 



Nectria ipomoeae Halsted is mentioned as an example of a species 

 furnishing many pitfalls. This is a cosmopolitan saprophytic ascomy- 

 cete which crosses the path of various specialists. This fungus is called 

 Nectria ipomoeae when isolated from Ipomoea, N. coffeicola when from 

 Coffea, N. cancri, when from canker spots of Theobroma, N. vandae 

 when from Vanda. 



Nectria discophora Mont, has been four times described as a new 

 species by Paul Hennings, as pointed out by v. Hohnel and Weese, 

 simply because it looked different when collected from various hosts in 

 different stages of its development. In pure culture all these stages 

 could be easily imitated by special treatment and the mistakes once 

 discovered lead to a remarkable simplification of the nomenclature. 



