1920] 



WILSON— CROWN -G A LL 



67 



PLATE VII 



Fig. i.— Alfalfa plant badly infected with crown-gall; X£. 



Fig. 2. — Single galls; Xi. 



Fig. 3. — Seedling infected in greenhouse, galls beginning to develop at 



crown; Xi. 



Fig. 4. — Section showing action of parasite upon wails of host cells in 



advanced stage; parenchyma tissue; X300. 



Fig. 5. — Plasmodium on border of gall; X300. 

 Fig. 6. — Sections of resting snores showing c 



laye 



wall; X130. 



Fig. 7. — Section of young gall on seedling showing cells of parasite in 

 host cells; some of former fused into tiny plasmodia, others in contact with 

 host nuclei; X300. 



Fig. 8. — Section of gall showing cavities and resting spores of parasite. 



PLATE VIII 



Fig. 9. — Unstained resting spore, view of hollowed surface; X750. 

 Fig. 10. — Unstained resting spore, side vie w; X750. 



Resting spore conforming to host cell in which it has developed; 



Fig. 



11. 



X750. 



Fig. 12. — Unstained resting spore showing marginal vacuoles; X750. 



Fig. 13. — Irregular relation of walls of resting spore; X1800. 



Fig. 14. — Unstained sporange when first put into hanging-drop culture; 



X750. 



Fig. 15. — Section of resting spore; may be stage just following resting 



period; X1800. 



Fig. 16. — Group of nuclei in sporange; chromatin in marginal aggrega- 

 tions; X1800. 



Fig. 17. — Division figures in sporange, apparently just preceding zoo- 

 spore formation; large nucleus destined to be nucleus of large zoospore ; X 1800. 



Fig. 18. — Spore formation about completed, unstained; note rupture of 

 outer wall; X750. 



Fig. 19. — Unstained sporange containing a few zoospores; most of those 

 formed already escaped through prominent opening; X750. 



Fig. 20. — Section of sporange just preceding formation of zoospores; 

 X1800. 



Fig. 21. — Section of sporange showing large nucleus which will be included 



in large zoospore; X1800. 



Fig. 22. — Marginal portion of sporange showing beginning of cleavage 



into zoospores ; X 1 800. 



Fig. 23. — Zoospores almost fully formed in sporange; X1800. 

 Fig. 24. — Nuclei of sporange showing nucleoles; X1800. 

 Fig. 25. — Zoospore just before exit from sporange ; X1800. 

 Fig. 26. — Xuclei of resting condition of spore. 



