218 PROCEEDINGS OF THE AMERICAN ACADEMY 



EXPLANATION OF FIGURES. 



[All magnified 330 diameters.] 

 PLATE I. 



Ravenelia glandulceformis, Berk, and Cui't. 



Fig. 1. A transverse section of the leaflet of Tephrosia virginiana, Pers. The 

 normal condition of the leaf tissue is seen at the left. The section 

 was cut with a hand razor after the leaflet had been softened in a 

 warm solution of potassic hydrate. 



Fig. 2. A head cut from the leaflet and mounted in alcohol to show the gen- 

 eral habit. 



Fig. 3. A spore-mass mounted in glycerine jelly, seen from above ; a, marginal 

 cells ; b, central cells. 



Fig. 4. A spore-mass mounted in alcohol, seen from above. 



Fig. 5. An abnormal head mounted in alcohol, seen from the side. Tlie cells 

 a, b, and c have thick brown walls. The stalk is broken off. 



Fig. 6. The cross-section of a spore-mass which has been treated with potassic 

 hydrate and mounted in balsam. Lateral cell, a ; external central 

 cell, b ; internal central cell, c 



Fig. 7. An internal and an external central cell from a head macerated in a 

 solution of potassic hydrate. 



Fig. 8. A transverse section of a head treated with alcohol, and mounted in 

 balsam. 



Fig. 9. A very ripe head mounted in alcohol and viewed from above. The 

 spore-mass has broken from the stalk, and the ruptured cysts project 

 beyond its periphery. 



PLATE II. 



Ravenelia gland id aformis, B, and C. 



Fig. 10. A side view of a head treated with a warm solution of potassic hydrate. 

 Fig. 11. A liead partially macerated in a warm solution of potassic hydrate, 



seen from the side. 

 Fig. 12. An optical section of a very young head, isolated by teasing a piece 



of leaf-tissue previously boiled in a solution of potassic hydrate. 

 Fig. 13. A head in a more advanced stage than the last, obtained by teasing. 

 Fig. 14. A side view of a still older head. 



Ravenelia sessilis, Berk. 



Fig. 15. A head treated with potassic hydrate. (Curtis Coll.) 

 Fig. 16. A head similarly treated. (Ravenel's Exsiccati.) 



Ravenelia Indica, Berk. 



Fig. 17. Side view of a head softened in potassic hydrate. (Curtis Coll.) 

 Fig. 18. A cross-section of a spore-mass mounted in balsam. (Mexico.) 

 Fig. 19. Side view of a head softened in a solution of potassic hydrate. 

 (Mexico.) 



