Abstract: Comparing　the　isolates　which　three　belong　to　Marssonina　brunnea　f．sp．monogermtubi　and　four　belong　to　Marssonina　brunnea　f．sp．multigermtubi，no　significant　difference　was　found　on　the　morphological　features　of　conidia　（shape，mean　dimension，size　and　septum　location）．But　there　are　much　difference　occourring　on　the　cultural　features　and　pathogenicity　between　the　two　specialized　forms．The　isolates　of　M．brunnea　f．sp．monogermitubi　possesses　the　characteristics　of　faster　colony　growth，　dark　reddish　conidiosorus　production　on　PDA　medium，　mostly　pathogenic　to　P．tomentosa　and　slightly 　pathogenic　to　P．×euramericana　Ⅰ45，　P．canadensis，　P．cathayana　and　P．simonii　by　artificialinoculation．The　isolates　of　M．brunnea　f．sp．multigermtubi，　however，has　the　characteristics　of　slowly　colony　radial　growth　and　　yellowishgreen　conidiosorus　production，　seriously　pathgenic　to　P．×euramericana　Ⅰ45　and　P．canadensis，　also　pathgenic　to　P．tomentosa，　P．cathayana　and　P．simonii．The　test　of　hyphal　anastomoses　showed　that　the　hyphae　which　of　the　same　specialized　form　can　anastomose　together．Hyphal　anastomoses　shall　not　occour　between　two　hyphae　which　come　from　two　different　specialized　forms．