110 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH SER. 
often go for a mile or more inland without seeing a single 
specimen, but when an exposed lava ridge or a barren field of 
lava is encountered, where conditions are such that very little 
other vegetation will grow, specimens will occur abundantly. 
The probable reason for this is that the species of Cereus are 
shaded out as soon as any considerable amount of other vegeta- 
tion appears. Plate VI. Endemic. 
C. sp.—BInpDLoE Ist.: Heller. Probably C. sclerocarpus 
acc. to Rob. (1), 180. No specimens of Cereus were seen by 
any of the members of our party when this island was visited. 
Opuntia Raf. 
O. galapageia Hensl. Mag. Zool. and Bot. I. 467, t. 14, f. 2 
(1837); Rob. (1), 180.—Axsrinepon IsL.: common on lava 
beds to 1000 ft., occasional above this elevation to 1300 ft. The 
specimens from the lower parts form trees 8-10 ft. high and 
have the branches closely arranged, giving the crown a very 
dense appearance, while those from the upper parts have the 
branches rather loosely arranged. In general the specimens 
from the upper parts are much infested with lichens, and have 
a more sickly appearance than do the specimens on the lower 
parts, (no. 3001). CHaAmprIon IsL.: specimens low, with very 
thick trunks, and apparently very much more abundant than on 
the adjacent shores of Charles Island, (no. 2098). CHARLES 
IsL.: abundant below 500 ft., occasional to 1300 ft. on the west 
side of the main mountain. One of the specimens from this 
place is peculiar in that the fascicles are made up mostly of. 
capillary bristles but in addition have one or two long pungent 
spines. There are fewer Opuntias here than on most of the 
other larger islands, a fact that is probably due to the presence 
of cattle, hogs, and burros which eat the smaller and less pro- 
tected specimens. Duncan Isu.: occasional at 450 ft., 
abundant around 1000 ft., especially on the floor of the main 
crater, occasional to 1250 ft. The specimens on this island 
have the branches openly arranged and often covered with 
various species of lichens. “See Plate X. GARDNER IsL. (near 
Hoop Isui.): an interesting variation of this species occurs 
here in that some of the specimens are stemless and have the 
branches procumbent. One individual of this kind was found 
growing immediately underneath a specimen with a stem 6-7 
