Rayner.—Obligate Symbiosis in Calluna vulgaris . 133 
Fig. 10. Normally infected seedling from unsterilized sand culture in tube as shown in Text- 
fig. 1. 282 days after planting. 
Fig. 11. Root mycorrhiza. Superficial cell of young root with hyphae. Camera lucida drawing 
from whole root, stained cotton blue in lactic acid. Zeiss, horn. imm. 3 mm. Compens. oc. 12. 
x 1620 diam. 
Fig. 12. Infection of leaf. Cells of the mesophyll with invading hyphae. m. — mesophyll cell 
of leaf ; h. = hyphae ; chi . — chloroplast. Camera lucida drawing from transverse section of shoot 
(Fig. 5). Zeiss, hom. imm. 3 mm. Compens. oc. 8. x 880 diam. 
Fig. 13. Infection of leaf. Mycelium in air-space of leaf, with crystals of calcium oxalate. 
C. — Cao ; h. = hyphae. Camera lucida drawing from longitudinal section of a fresh leaf. Leitz 
obj. 6. Zeiss compens. oc. 12. x 880 diam. 
Fig. 14. Sterile seedling growing in nutrient agar and artificially infected from a pure culture 
of the mycorrhizal Fungus. Ninety-five days from sowing ; twenty-seven days after planting and 
inoculation, f. — limit of fungal growth in agar. This seedling subsequently reached a height of 
6 cm. x i|. 
Fig. 15 a. Sterile control seedling in nutrient agar. Ninety-five days from sowing; twenty- 
seven days after planting. No,subsequent growth took place in this or other controls, x i|. 
Fig. 15 b. Sterile control seedlings on filter-paper. Same age as Fig. 15 a. 
Fig. 16. Sterile seedling, infected artificially from a ‘ strong ’ culture of the mycorrhizal Fungus 
in nutrient agar. Ninety-five days from sowing, twenty-seven days after planting, h. = mycelium 
growing out from shoot. 
Fig. 17. Sterile seedlings on filter-paper, inoculated from a pure culture of the mycorrhizal 
Fungus supplied with distilled water only (cf. Fig. 18). Ninety-five days from sowing ; twenty-one 
days after inoculation, f. = Fungus. 
Fig. 18. Sterile seedlings of same age under similar conditions, but supplied with a dilute 
nutrient solution extract of distilled water. Seedling completely parasitized and destroyed ; Fungus 
vigorous and forming pycnidia. 
Fig. 19. Mycorrhizal Fungus. Pure culture on rice. Five weeks. Diameter 4*5 cm. 
Fig. 20. Mycorrhiza] Fungus. Pure culture on Calluna-vx .tract gelatine. Fifteen days. 
Fig. 21. Mycorrhizal Fungus. Mycelium from five-weeks’culture on nutrient agar, x 250 diam. 
