THE VEGETATION OF THE SUMMIT OF MOUNT HAMILTON. 79 
others were enumerated out of a small collection brought to 
me by Mr. C. T. Blake of Berkeley, a botanical amateur of 
keen eye who does more or less good service in botany where- 
ever he goes on a vacation tour. As to the ground intended 
to be covered by the catalogue, I may say that it begins at no 
very precisely marked point, but in a general way embraces 
the land lying above the line of the Aquarius Road on the 
north side, and descends to about the same elevation on the 
southward slope, extending eastward to the Joaquin Murrieta 
Springs. 
The relative aridity of Mount Hamilton as compared with 
such mountains as Diablo and St. Helena, is indicated by the 
absence of everything which can be called a forest. Such 
oaks and pines as are of arborescent dimensions are too much 
scattered to constitute even a grove anywhere, and represent 
those species only which belong to the dry districts. The 
Coast Range oaks which, under more favorable conditions 
become large trees, are here found on the north side only, 
and near the summit, forming low thickets not much exceed- 
ing a man’s height. The genus Ceanothus, which in other 
and less arid mountain districts both of the Coast Range and 
the Sierra Nevada, often makes up a great proportion of the 
dense brushwood that covers the slopes and even the lower 
summits, seems to be wholly absent from Mount Hamilton; 
and even the Buckthorn is found to be the Rhamnus tomen- 
tella of the dry interior of the State, and not the R. Cali- 
fornica of the moist seaboard hills and mountains. Equally 
strong botanical evidence of a dry atmosphere is found in the 
abundant development of the genus Hriogonum, the species 
of which are most numerous in the very dry region of the 
Great Basin east of the Sierras, few in the Californian Coast 
Range, and of a somewhat surprising number on the higher 
slopes of Mount Hamilton, where most of the species are 
representatives of more southerly districts, and have here, 
at least in some cases, their northern limit of distribution. 
Although, as above noted, our list is not like to prove a 
complete one, it is fairly representative of the flora of this 
