560 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



Fig. 7. Pure culture, three days old, of Colletotrichum alramentarium isolated 

 from silver scurf spots of white potato. 



Fig. 8. Pure culture three days old of Colletotrichum atramentarium obtained from 

 Dr. O'Gara. 



Figs. 9 and 10. Colletotrichum atramentarium transfers from Figs. 7 and 8, showing 

 zonations of sclerotia and the abundance of the latter in pure culture. 



Fig. i I . Cross-section of a spot of silver scurf of white potato to show relationship 

 of the fungus Spondylocladium atrovirens Harz to the host tissue. Notice the fungus 

 is confined to the epidermis of the tuber. 



Fig. 12. Cross-section of a silver scurf spot of a white potato tuber showing sclerotia 

 of Colletotrichum atramentarium (Berk. & Br.) Taub. 



Fig. 13. Conidiophores and conidia of Colletotrichum atramentarium. 



Figs. 14-16. Germinating spores ot Colletotrichum atramentarium. 



Figs. 17 and 18. Germinating spores of Colletotrichum alramentarium, showing forma- 

 tion of appresoria at tip of germ tube. 



Fig. 19. Single sclerotium with setae of Colletotrichum atramentarium, showing its 

 relationship to the epidermis of a killed white potato vine. 



Figs. 20 and 21. Sclerotia and ascervuli of Colletotrichum atramentarium on dead 

 potato vines. 



Fig. 22. Surface black mycelium of Colletotrichum atramentarium in pure culture. 



Fig. 23. Hyaline deep-growing mycelium of Colletotrichum atramentarium in pure 

 culture. 



Figs. 24 and 25. Showing variations in sizes of spores of Colletotrichum atramen- 

 tarium in pure culture. 



Fig. 26. Germinating spore of Spondylocladium atrovirens breaking through the 

 epidermis of the host. 



Figs. 27-29. Germinating spores of Spondylocladium atrovireiis Harz. 



