FORESTRY IN THE EXHIBITION AT NURNBERG. 235 
branch of a dicotyledon the opposite is the case. This may be 
seen by cutting off horizontal branches of the two classes of 
trees named. In the case of the conifer, the pith will be found 
to be nearer the upper than the lower side of the section, while 
in the dicotyledon the shortest radius is on the under side. The 
horizontally disposed roots of trees (the spruce is a good 
example) also show marked eccentric growth, but in their case 
the character of the eccentricity is always the same, the greatest 
growth, and therefore the longest radius, being on the upper 
side. It is evident that the upper side of a root is subjected to 
less pressure from the soil than the lower side, and as the 
cambium makes most wood where the pressure is least, the 
greatest growth is found in a root precisely where it is to be 
expected. But the variable condition of things in the branches 
of conifers and dicotyledons has always been a puzzle to botanists, 
and no satisfactory explanation is yet available. Nor is it quite 
easy to say why, in a tree grown on a steep hill-side, greater 
growth should be shown on the side away from the hill. 
A fine series of young trees has been prepared to illustrate 
the fact that most of the roots of forest trees live in intimate 
association with delicate fungus mycelia {(mycorhiza). This 
relationship has not been fully worked out, but it is evident that 
it is of the same character as the symbiosis that exists between 
the roots of leguminous farm and garden crops and _ bacteria. 
Sometimes the mycelia work their way between the cells of the 
epidermis and cortex (e.g., Scots pine, spruce, beech, oak, birch), 
and roots so affected are called ectotropic mycorhiza. In other 
cases the fungus strands actually penetrate the cells of the root 
(endotropic mycorhiza), examples of which are Zhuya occidentalis 
and yew. 
In Bavaria, as in this country, oak bark has experienced a 
great drop in price during the past twenty years, the price per 
cwt. having fallen from 4s. 9d. in 1885 to 1s. gd. in 1905. Con- 
currently with this decrease in value, the returns from coppice 
woods have steadily declined, being 13s. 9d. per acre in 1885 
and 8s. in 1905. But during the same period the returns from 
high-forest have shown a satisfactory increase, having risen 
from gs. per acre in the former year to 11s. 9d. in the latter. 
The cause of the fall in price of home-grown bark is the large in- 
crease in the importation of tanning materials, notably quebracho 
wood, specimens of which, and of the extract, were on view. 
