ABSTRACT 



Selection of young stem sections free of external 

 injury and the reduction of physical and/or chemical 

 damage to tissues during their preparation, steriliza- 

 tion, and excision were the most important factors gov- 

 erning survival and growth of healthy and diseased 

 conifer tissues in vitro. Most (75-98 percent) primary 

 explants from properly selected stems, prepared as 

 described, survived and produced subsequent growth on 

 suitable media. Proliferation of the rust {Cronartium 

 ribioolaJ. C. Fisch. ex Rabenh. ) occurred in 75 per- 

 cent of the surviving blister rust-infected primary ex- 

 plants from western white pine (p^n^^ montiaola Dongl.). 



