Description of Plates. 3 2 i 



interspace between the inner surface of the primary embryonic sheath and 

 the cuter surface of the embryo of a rye plant. x 375. \\'olff. 



Fig. 3. — Promycelial spore of Tilktia IcEvis entering the primary sheath 

 of a wheat plant and invaginating a sheath of cellulose. x 600. Wolff. 



Fig. 4. — Spore-forming hypha of Tillctia tritici from wheat, showing the 

 budding of the spores ; from an ovary i mm. long. X 900. Von Waldheim. 



Fig. 5. — The extremity of a spore-forming hypha of the same, showing 

 two spores in different degrees of development. X 500. Von Waldheim. 



Fig. 6. — Transparent single-contoured spore of the same, with shrivelled 

 remains of the spore-forming hypha. X 500. Von Waldheim. 



Fig. 7. — Teleutospore of 7'. tritici germinating after forty-eight hours in 

 water. x 500. C. B. P. 



Fig. 8. — The same more advanced, showing the H -shaped spores (primary 

 promycelial spores conjugated), two of which have already fallen away from 

 the promycelium. x 300. C. B. P. 



Figs. 9, 10. — Primary promycelial spores conjugated, empty, and septate, 

 each pair of which has produced a secondary promycelial spore. x 300. C. 

 B. P. 



Fig. II. — Two secondary promycelial spores conjugating. x 350. C. 



B. P. 



Fig. 12. — The same a little later. A germ-tube has been given off from one 

 of the spores, x 350. C. B. P. 



Fig- 13. — A single unconjugated secondary promycelial spore giving off a 

 germ-tube, x 350. C. B. P. 



I'ig. 14. — Mycelium from a single primary promycelial spore in nahrlosung 

 producing conidia. x ico. Reduced from Brefeld. 



Fig. 15- — A small portion of the same more highly magnified. x 357. 

 After Brefeld. 



Plate VII. 



Fig. I. — Ustilago segetum. Teleutospore germinating in water after sixteen 

 and a half hours, x 500. C. B. P. 



Fig. 2. — The same, with a secondary promycelial spore produced from a 

 primary while still attached to the promycelium. x 500. C. B. P. 



Fig. 3.— A promycelium of the same forming a buckle joint. x 500. 



C. B. P. 



Fig. 4. — A promycelium of the same forming a bow joint, x 500. After 



Brefeld, 



Fig. 5. — Two promycelia conjugating. X 500. C. B. P. 



Fig. 6. — A promycelium growing out into a germ-tube. X 500. After 

 Wolff. 



Fig. 7. — Two promycelia given off from one teleutospore. X 500. C. B. P. 



Fig. 8. — Yeast-spores produced from a promycelium in nahrlcisung (three 

 days). X 500. C. B. P. 



Fig. 9 — A promycelium with a buckle joint and secondary promycelial 

 spores in exhausted nahrlbsung (twelve days). X 500. C. B. P. 



Fig. 10. — A yeast-spore colony, produced from a single teleutospore. 

 X 500. Brefeld. 



Fig. II. — Promycelial spores conjugating, x 500. C. 1!. P. 



Y 



