The Ecology of Calluna vulgaris 
77 
Description of the Photographs on Plate III, Illustrating 
Miss Rayner’s Paper on “The Ecology of CALLUNA VULGARIS." 
Fig. la. Calluna seedlings from “ heather ” soil, showing normal root 
and shoot development; six months old. 
Fig. lb. Calluna seedlings from “heather” soil treated with carbon 
bisulphide vapour; six months old. The more vigorous growth as compared 
with Fig. la is less marked than at an earlier stage. 
Fig. lc. Calluna seedlings from “chalk” soil, showing arrest of root 
and shoot development; six months old. 
Fig. Id. Calluna seedlings from “chalk” soil treated with carbon 
bisulphide vapour ; six months old. As compared with Fig Ic, root develop¬ 
ment is more normal. 
Fig. 2a. Apex of a young Calluna root from “heather” soil, showing 
normal conditions. 
F'ig. 2b. Apex of Calluna root of same age from “chalk” soil, showing 
abnormal condition with bacterial investment. 
Fig. 3. Part of root apex shown in Fig. 2b, more highly magnified, to 
show bacteria in sheath. 
Fig. 4a. Calluna seedling in “heather” soil watered for six months with 
an extract of “ chalk ” soil. 
Fig. 4b. Control—similar seedling watered during the same period with 
distilled water. 
Fig. 5. Calluna seedling from “chalk” soil, watered for six months with 
an extract of “heather” soil. Control seedlings in similar soil watered with 
distilled water all died before the end of the experiment. Fig. lc shows 
surviving seedlings of the same age in this soil from another series of 
experiments. 
Fig. 6. Mycelium from fungal colonies surrounding seeds, in agar 
cultures of “ chalk ” soil, to show investing sheath of bacteria. 
