198 BOTANICAL GAZETTE, [August, 
interesting material for the study of the durability and stability of 
species. 
The short interval of ten years between Dr. Palmer’s and Mr. 
Greene’s visit to Guadalupe points strongly to the possible ex- 
tinction of some species, the introduction or genesis of others 
Notably in the cases of Hosackia grandiflora, Juniperus Cali- 
fornica var. osteosperma and Polypodium Scouleri,* we appar- 
ently have examples of extinction proceeding at a rate sufficiently 
rapid to bring it within the observation of a single generation of 
On San Clemente I noted in great profusion the lifeless stem 
and root of a Cotyledon and can readily credit the statement 
made to me that only eight years ago the island was fairly car- 
peted with this plant. A season of drouth drove the sheep to 
feed upon it, and it is easy to conceive that a succession of better 
years by affording more wholesome pasture and thus diverting 
the attention of the stock might enable the species from the few 
remnants left upon wholly inaccessible rocks to once more regain 
its pristine supremacy. 
A species reduced to the verge of annihilation, or to so criti- 
cal a condition as the Guadalupe Juniper, might, through a short 
succession of seasons of ample rainfall, be readily restored to its 
original vigor. ‘ 
hese somewhat forced illustrations are used to emphasize the 
fact that on little known islands the utter extinction of species is 
and will be a difficult matter to establish beyond a doubt. The 
same remarks apply in reference to the supposition of the recent 
introduction or creation of new species; some in such abundance 
now as makes it seem improbable that they should have escaped 
the keen scrutiny of the expert collector; yet in default of affirm- 
ative proof to the contrary, we must ascribe their absence to the 
first collector’s omission rather than to the hypothesis stated. 
Though entirely out of order to criticise any part of Mr. Wat- 
son’s paper at this late day, I can not but express surprise that 
80 conservative an author in drawing his final inferences should 
lay particular stress upon the absence of certain orders and genera 
of plants upon Guadalupe. 
_ Due recognition does not seem to have been given to the fact 
that Dr. Palmer’s collections were made in the spring and early 
summer, and hence (if the flora be at all Californian) would en- 
tirely fail to illustrate any of the later flowering Composite or 
Polygonacee. 
asinine 
SBull. Cal. 1. ¢., p. 210. 
¥ 
