l896-97'] THE GAMETOPHYTE OF BOTRYCHIUM VIRGINIANUM. 29I 



EXPLANATION OF PLATES. 

 Plate L 

 Fig. I. — Youngest prothallium found, a?-, antheridial ridge. x 8. 



Fig. 2. — An older stage in which the antheridial ridge has become more marked. 

 X i6. 



Fig. 3. — A considerably older gametophyte on which is a developing embryo, em. 

 The antheridial ridge, ar, is particularly prominent. This prothallium is lithographed 

 from a photomicrograph. x 7. 



Fig. 4.— a lobed prothallus from a photomicrograph. x 4. 



Fig. 5. — From a photomicrograph ; represents a younger phase in which the root- 

 hairs are abundant. x 8. 



Fig. 6. — A lobed prothallus lithographed from a photomicrograph, and bearing two 

 embryos, em"^ and ei>i-. x 4. 



Fig. 7. — A young sporophyte showing the first root. x 8. 



Fig. 8. — A young sporophyte showing two roots ; the cotyledon is still unex- 

 panded. x 4. 



Fig. 9. — A young sporophyte with the primary root and the cotyledon, x i. 



Fig. 10. — A stouter sporophyte with three roots and the cotyledon. x %. 



Fig. II. — A lobed prothallus bearing two advanced sporophytes. x i. 



Fig. 12. — A prothallus bearing two further advanced sporophytes. x ^. 



Fig. 13.— a bifurcated sporophyte still attached to its prothallium. x 4. 



Fig. 14. — An eight year sporophyte still attached to its prothallium. x Y^. 



Fig. 15. — A cross-section of a prothallus showing the antheridial ridge, x ; the 

 fungiferous cells, /' .■ and the uninfected cells, a. At y are the archegonia, and h, root- 

 hairs, x 16. 



Fig. 16.— a long-section of the prothallus ; lettering the same as in the preceding 

 figure, ap, apical region. x 16. 



Fig. 17.— Apical meristem. «, apical cell of prothallus. x 250. 



Fig. 18.— Showing the penetration of the fungus into the gametophyte. i; root- 

 hair ; 1) and d, superficial cells, in which the cutinized sheaths have been produced ; 

 X, fungiferous cells ; j, uninfected cells ; a, conidia. x 250. 



Fig. 19. — Fungiferous cells ; a, with purely filamentous mycelium ; /' and c, mixture 

 of filamentous and vesicular mycelium. x 600. 



Fig. 20. — Cell showing the formation of vesicles, /, as outgrowths from a 

 hypha, h. x 1,000. 



