DISEASES OF PLANTS. 653 



cause of tbe disease lias been established by means of repeated inoculations, 

 reisolatious, and reinoculatious. 



Tbe fungus causing tbe disease, S. tumefaciens, has been isolated from knots 

 on lime and orange trees, and small knots have been also obtained from 

 pomelo, lemon, tangerine, and Citrus trifoliata. The fungus penetrates the 

 tissues far beyond the original point of infection, and. a badly infected tree 

 is a mass of tumors, sometimes not more than half an inch separating them. 

 On (he other hand, there may be considerable distance between two secondary 

 tumors with no external evidence of the fungus, but microscopical examina- 

 tion reveals its presence in small quantities throughout the intervening portion 

 of the stem. Occasionally an abnormal number of new shoots grow from 

 the knots, forming witches' brooms, and this is said to be a characteristic of 

 the disease under favorable conditions. Ultimately that portion of the branch 

 above the knot dies. 



Notes are given on the life history of the fungus, which w'as found to live for 

 several years in the host. 



It is suggested that affected limbs be removed, cutting them well below the 

 lowest knots, and that badly diseased trees be uprooted and burned. 



Citrus scab, H. S. Fawcett (Florida Sta. Bui. 109, pp. Jf7-60, figs. S).— A de- 

 scription is given of the citrus scab, due to Cladosporium citri. This fmigus 

 has been isolated from sour orange leaves and cultivated, and infection experi- 

 ments have been made demonstrating that it is the cause of the trouble 

 described. 



The fungus seems particularly injurious to sour orange and lemon sprouts, 

 and the author recommends the destruction of these, together with spraying with 

 ammoniacal copper carbonate or Bordeaux mixture. The copper carbonate solu- 

 tion is preferred since it usually does not cause an increase of scale insects as 

 sometimes follows the use of Bordeaux mixture. "Where the disease is vei-y 

 prevalent the first spraying should be done soon after the petals fall, followed by 

 a second in 2 weeks or a mouth, and a third at a similar interval if necessary. 

 New gi'owth which comes out at unseasonable times and late bloom, locally 

 known as "June bloom," are said to be most subject to infection, and these 

 should be cut out and destroyed. 



A bibliography is appended. 



Notes on some diseases of trees in our national forests, II, G. G. Hedgcock 

 {Phytopathology, 2 (1912), No. 2, pp. 73-80). — In continuation of a previous 

 account (E. S. R., 23, p. 4.jU), the author describes some diseases of deciduous 

 and coniferous trees. The principal fungi attacking deciduous trees enumerated 

 are Polyporus dryopMlus, P. texanus, P. sulphureas, Foincs igniarius, F. evcr- 

 hariii, F. nigricans, F. applanatus, F. fasciatus, F. fravlnopMlus, and F. 

 rohiniw, while on coniferous trees he notes the occurrence of Trametes pini.. 

 P. schwcinitzii, F. laricis, Echinodontiuin tinctorium, P. sulphureus, P. amarus, 

 Lenlinus lepidcus, and Hydnum coralloldcs. 



The chestnut bark fungus, Diaporthe parasitica, C. L. Shear [Phyto- 

 paihology, 2 (1912). No. 2, pp. 88, 89). — A brief discussion is given of the generic 

 and specific identification of this organism and its relation to some other fungi. 



Some observations on experiments with the chestnut bark disease, J. F. 

 Collins (Abs. in Phytopathology, 2 (1912), No. 2, p. 97). — The author points out 

 that the mycelium of this fungus, contrary to common belief, can penetrate and 

 continue to grow in the wood under an old diseased spot after the infected bark 

 has been removed and the surface of the wood treated with tar, paint, etc., 

 und that fruiting pustules may at times be produced in abundance on bare wood ; 

 that summer spores are not as liable to be blown about by the wind as has been 



