The territory in question is divided naturally into three parts:
1. The northern part of the peninsula of San Francisco, with an undulating and hilly surface, consists of drifting sand, with a small per centage of humus mingled with it.
2. The Oakland Hills, running N. 54° W. mag., from the Bay of San Pablo to San Leandro, a distance of twenty-three miles, with the adjacent slopes and valleys. Heavy clayey soil predominates; but where shrubs and trees grow it is mostly a loose, light, and slightly sandy soil.
3. That part of Marin County between San Rafael, the head of Tomales Bay and Bolinas Bay, forming a triangle, with a hilly surface, the ridges running N. 54° W. mag. Soil a heavy clay, in the valleys and on bare hills; or a light, slightly sandy loam among shrubs and trees.
In all parts a metamorphic sand-stone underlies the soil.
Berberis (Mahonia) Aquifolium Pursh.
A low evergreen shrub, three to four feet high, not gregarious; in clay soil on the hill sides; rare.
Dendromecon rigidum Benth.
A shrub with slender upright branchlets, four to six feet high, rare; on white sand-stone, Oakland hills, third range eastward, not gregarious.