418 ALLAN KLINGSTROM 



differences in aeciospores and germ tubes, and to indications of dif- 

 ferences in amino acid content of aeciospores of the different strains 

 of the fungus . 



An account is also given of an inoculation experiment with different 

 P. silvestris progenies with varying degrees of susceptibility. 



LITERATURE CITED 



Bergman, F. 1954. Om skogstrSdens sjukdomsresistens och dess utnvttiande 



inom skogstrSdsfo'radlingen, p. 70-98. In Fo"ren. for vaxtfo'radling av 



skogstrad, Arsberattelse 1953. 98 p. 

 BoTmer, P. 1952. Der kieferndrehpilz - eine ernste Gefahr fdr Kiefern- 



kulturen. Allg. Forstzeitschr . 46: 471-475. 

 Eklundh Ehrenberg, C. 1963. Genetic variation in progeny tests of Scots 



Pine (Pinus silvestris L.). Stud. Forest. Suec. 10: 1-135. 

 Hattemer, H. H. 1965. ZUchtung der Kiefer auf Resistenz gegen 



Melampsora? Forstarchiv 36: 8-11. 

 Hiratsuka, Y. 1968. Morphology and cytology of aeciospores and aecio- 



spore germ tubes of host -alternating and pine-to-pine races of 



Cronartium flaccidwn in northern Europe. Can. J. Bot . 46: 1119-1122. 

 Illy, G. 1966. Note on the resistance to pine twist rust caused by 



Melampsora pinitorqua in the offspring of Pinus pinaster, p. 125-126. 



In Gerhold, H. D, , et al. (ed.), Breeding pest-resistant trees. 



Pergamon Press, Oxford. 505 p. 

 Kardell, L. 1966. Nagra observationer om knackesjukeangrepp pa tall i 



Vasterbottens inland. Sveriges skogsvlrdsfo'rbunds tidskrift 7: 649-663, 

 Klingstrom, A. 1963. Melampsora pinitorqua (Braun) Rostr. - Pine twist 



rust. Stud. Forest. Suec. 6: 1-23. 

 Klingstrom, A. 1969. Melampsora pinitorqua (Braun) Rostr. on progenies 



of Pinus silvestris L. and in relation to growth regulating substances. 



Stud. Forest. Suec. 69: 1-76. 

 Regler, W. 1957. Der Kieferndrehrost {Melampsora pinitorqua) eine 



Wirtschaftlich wichtige Infektionskrankheit der Gattung Pinus. Beitr. 



zur Pappelforsch. 2: 205-234. 

 Rennerfelt, E. 1954. Biologische Untersuchungen tlber den Kiefemdreher 



Melampsora pinitorqua (Braun) Rostr., Vol. 3, p. 705-711. In 11th 



IUFRO Cong. Proc, Munich, 1954. DVFFA, Munich. 

 Schu'tt, P. 1964. Zum Drehrostbefall an Kiefern. Unterschiede in der 



Starke des Melampsora pinitorqua-Re falls zwischen Herkiinften und 



zwischen Einzelstammnachkommenschaften der Kiefer. Forstarchiv 35: 



51-53. 

 Schu'tt, P. 1965. Zur ziichterischen Nutzung der Krankheitsresistenz von 



Waldbaumen. Forstarchiv 36: 51-53. 

 Ziller, W. G. 1965. Studies of Western Tree Rusts VI. The aecial host 



ranges of Melampsora albertensis , M. medusae and M. oooidentalis . 



Can. J. Bot. 43: 217-230. 



FLOOR DISCUSSION 



Discussion of the above paper appears after the paper by Dr. 

 Steenackers that follows. 



