CENTRAL STATION TREE-PLANTING ON A HILLTOP. 119 



English oaks; three are 16, 20, and 23 inches, respectively, above the 

 ground. Of the fifteen trees, six will average fully 10 feet in height, 

 while the others are more or less scrubby. Both cork and English oaks 

 are very healthy, and seem as well established here as any native tree in 

 the adjacent gulches. The oaks are on a dry western slope, where the 

 pasturage was turning brown May 24th. 



The only profit possible from oak plantations in such soil as this 

 must come from trees constantly side-pruned and cultivated for several 

 years. If a shrubby growth can be avoided, both the English and the 

 cork oaks will thrive here. A plantation of twenty or more acres of cork 

 oaks would give the matter a thorough practical test. 



Other Trees. Pines of several species planted here made good growth, 

 reaching in some cases a girth of 15 inches, but were broken down by 

 cattle. Monterey cypresses, though still alive, are now mere clumps 

 with dozens of scattered stems. Cork-bark elms failed. Two California 

 poplars (Populus Fremonti) are growing well, but have no economic 

 value as compared with the eucalypts, acacias, and oaks. 



Conclusions. The poorest part of the grove is at the extreme west, 

 exposed to the full sweep of the wind. Gophers and cattle, not drought 

 or native vegetation, destroyed most of the trees which died. Fenced 

 from cattle and given some cultivation the first few years, the growth 

 would have been much greater than it is. In a larger plantation, too, 

 the mutual shelter afforded by the young trees would be considerable. 



But in spite of all drawbacks, Acacia decurrens, eucalypts, and oaks 

 are well established here. Land as steep as this is rented at from fifty 

 cents to a dollar an acre per annum, and is only used for pasturage. 

 There are thousands of acres of such land in the Coast Range within 

 fifty miles of San Francisco that will pay interest on a much higher 

 valuation, if used for growing firewood, not to say a better quality of 

 timber. As the general illustration (Plate 21) shows, the grove of oaks, 

 eucalypts, and acacias, though small, covers the ground well, is healthy, 

 and gives good evidence of the value of these hilltops for tree growth. 

 On even steeper slopes and on the very crest of the Coast Range, 

 numerous groves of blue gums exist which are now yielding profitable 

 returns. Larger forests should therefore be planted, and other species 

 of eucalyptus, also the wattle acacias, as well as oaks, should be given 

 consideration. 



NOTE* ON THE COMPOSITION OF THE ADOBE SOIL OF THE HILLTOP. 



BY E. W. HILGARD. 



The soil of the hilltop where the grove is situated is a very hard and 

 black adobe clay, cracking open when dry, breaking up in lumps, and 

 very difficult to remove, even with a pick. Samples were taken to a 

 depth of three feet in a representative part of the grove, and those of 

 the first and third feet subjected to a mechanical and chemical analysis 

 by Prof. Loughridge and Mr. Triebel in the station laboratory, with the 

 results given below. 



There was in each sample from 12 to 15 per cent of coarse grits and 

 rock fragments, which was sifted out and the analysis made of the fine 

 earth having a diameter of one half millimeter and less. 



