74 
W. B. McDOUGALL 
24. Stahl, E. Der Sinn der Mycorhizenbildung. Jahrb. f. wiss. Bot. 34: 539. 1900. 
25. Ternetz, C. Ueber die Assimilation des atmosphaerischen Stickstoffes durch 
Pilze. Jahrb. f. wiss. Bot. 44: 353. 1907. 
EXPLANATION OF FIGURES IN THE PLATES IV-VII 
All figures, except i, 11, and 12, were drawn with camera lucida. 
Fig. I. A root with ectotrophic mycorhizas. 
Figs. 2-6. Cross sections of ectotrophic mycorhizas. Fig. 2, form i, from 
Carya ovata. Fig. 3, form 2, from Carya ovata. Fig. 4, form 3, from Quercus alba. 
Fig. 5, form 4, from Quercus alba. Fig. 6, form 5, from Larix laricina. 
Fig. 7. Portion of cross section of heterotrophic mycorhiza from Tilia showing 
hyphae (a) which have entered the cortical cells of the root. 
Fig. 8. Longitudinal section of ectotrophic mycorhiza of Quercus showing root 
tip covered by fungous mantle. 
Fig. 9. Enlarged section of ectotrophic mycorhiza of Quercus alba showing 
hyphae (a) penetrating between the cortical cells of the root. 
Fig. 10. Section of immature ectotrophic mycorhiza of Tilia americana showing 
root tip still uncovered and hyphae (a) just beginning to penetrate between the root 
cells, b = outer portion of epidermal wall. 
Fig. II. Diagram showing cortical root cells (a) surrounded by fungous tis- 
sue (&). 
Fig. 12. Root with endotrophic mycorhizas. 
Fig. 13. Tangential section of endotrophic mycorhiza of Acer rubrum. 
Fig. 14. Longitudinal section of endotrophic mycorhiza showing the con- 
striction between two beadlets. 
Fig. 15. Enlarged cells containing endophyte. 
Fig. 16. Cells with endophyte curled around nucleus. 
Fig. 17. Cell containing a vesicle. 
Fig. 18. Cell with endophyte showing swellings of hyphae. 
Fig. 19. Hyphae within root-hairs. 
