DISEASES OF PLANTS. 707 



The active means suggested for preventing the disease is the exter- 

 miuation of the organism causing it. This consists in cutting back a 

 few inches into the sound wood, and burning every particle of the dis- 

 eased tissue while the trees are dormant. Xot only must all pear trees 

 be looked after, but all related trees, since they, too, are subject to the 

 disease. Cutting out blighted twigs during the season is also efficient 

 in i)reventing the rapid spread of the disease, but only when all traces 

 of blighted growth has been removed will the prevention be secured. 



Leaf spot of pear, G. F. Atkinson {Garden and Forest, 10 {1897), 

 No. 470, pp. 73, 74). — From observations made during the past 2 or 3 

 years the author thinks what is usually (;alled the leaf spot of pear is 

 not due wholly to Untomo.sporinm maculatum, but in perhaps the major- 

 ity of cases is due to a difi'erent parasite. In searching fallen leaves 

 that had lain on the ground all winter for the fungus the Entomospo- 

 rium was not found, but SpJuvrella sentina and 8. pyri were abundant. 

 Critical examinations made of spotted leaves in a nursery during 1805 

 revealed in the older spots the saprophytic Cladosporium herbarum and 

 Pleospora herbarum, while the young spots revealed abundant speci- 

 mens of Septoria. The ISeptoria sjDots greatly resemble those of the 

 Entomosporium, but a careful examination shows they are somewhat 

 larger and inclined to become angular in outline and elongated, while 

 the Entomosi)orium spots are nearly circular. Examinations made of 

 many orchards and of much material seem to indicate that Septoria is 

 the cause of most trouble. 



The subject is to be studied further, and a request is made for mate- 

 rial from different localities. 



A rust and leaf casting of pine leaves, B.T.Galloway {Bot. Gaz., 

 22 {lS9(i), Xo. 6, pp. 133-153, ph. 2, fi(js. 3). — The author has made an 

 extensive study of a rust of the scrub pine {Pinus virginiana). This 

 fungus, Coleosporium piiii,^ is rather abundant and causes considerable 

 injury to the trees, and this paper is an important contribution to its 

 life history. 



The author summarizes his investigations as follows: 



"(1) Coleosporium piiii occurs abuuilantly in Maryland, Virginia, and the District 

 of Columbia, attacking only Pinus rirfjiiiiana. 



"(2) It requires 12 months to complete tlie development of this fungus, and dur- 

 ing a large part of that time it does not seriously interfere with tln^ functions of its 

 host. 



"(8) The fungus is disseminated by means of sporidia, which develop <mly during 

 wet weather. 



"(4) From the leaves on which they are borne the sporidia are washed or drop to 

 tlie young needles just showing tlieir tips, which they infect. No evidence of this 

 infection, however, is apparent for 2 or 3 months. 



"(5) Regardless of the season, there is a marked similarity in the time of the 

 appearance of the sporidia and the time of the aiii>earance of the young leaves. 



"(<)) Before the fungus ruptures the cortical tissue evaporation from tlie diseased 

 areas is less thau that from healthy parts of the same leaf. This is due to the per- 

 manent closing of the stomata and may result in keeping the diseased parts alive 

 longer than the healthy in case the leaf or branch is removpd from the tree. 



'Jour. Mycol., 7 (IbW), p. 41, 



