PREFACE. 
The territory to which this book applies extends 
from Sonoma to Santa Clara, and from Niles to 
the Pacific Ocean. 
Since the year 1884, when the Synopsis of Genera 
was published, there have been added several 
genera, which up to that time had escaped obser- 
vation. Continued investigations will lead perhaps 
to the discovery of some more; certainly, they will 
lead to the addition of species hitherto unobserved 
in the territory. I have followed as much as pos- 
sible the admirable work of Asa Gray and Sereno 
Watson “Botany of California,” and from their 
views I have deviated only when opportunities 
for studying the plants from specimens growing on 
the spot afforded to me ample grounds for a view 
differing from that expressed by recognized au- 
thorities. 
As to many of the species characterized in this 
book, there exists still a considerable degree of 
uncertainty. Many of our Californian species split 
into numerous variations, which mingle frequently 
with variations of related, equally variable species. 
Some of these variations owe their existence to hy- 
bridization; and this circumstance is probably the 
reason why several species described and charac- 
terized by different authors have not been found 
