84 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH SER. 
From the above it can be seen that if formal differences occur 
in this species, such differences are not confined to a single 
island, as it often happens that specimens from different parts 
of the same island show quite as marked variations as do speci- 
mens from different islands. 
BURSERACEAE 
Bursera L. 
B. graveolens (HBK.) Trian. & Planch. Ann. Sci. Nat. 5, 
XIV. 303 (1872). Elaphrium graveolens HBK. Nov. Gen. & 
Sp. VII. 31 (1825). B. graveolens Trian. & Planch. 1. c.; 
Rob. (1), 159.—Axsinepon IsL.: common trees to 1000 ft., 
below 400 ft. they are small and scattered, (no. 1762). ALBE- 
MARLE Ist.: Banks Bay, common trees to 1700 ft., according 
to F. X. Williams; Cowley Bay, small trees above 400 ft., com- 
mon trees, 3-4 inches in diameter and 12-15 ft. high, around 
1200 ft., large spreading trees much infested with Usnea lon- 
gissima above 2000 ft.; Elizabeth Bay, Snodgrass and Heller; 
Iguana Cove, occasional small trees to 400 ft. The small size 
and scarcity of this species here may be due to the more moist 
conditions which prevail, (no. 1765); Tagus Cove, common 
trees in tufaceous soil on the lower parts and on the sides of 
the mountain to 2000 ft.; Villamil, low spreading trees com- 
mon to 550 ft. BARRINGTON IsL.: small trees, leafless in Octo- 
ber and July, much infested with Roccela peruensis. BINDLOE 
IsL.: northeast side, common trees in tufaceous soil. CHARLES 
IsL.: common trees to 1000 ft. CHATHAM IsL.: Basso Point, 
common trees to above 1000 ft.; Sappho Cove, common trees 
to above 800 ft.; Wreck Bay, common trees to 700 ft. CuL- 
PEPPER IsL.: low spreading trees, apparently of this species, 
were seen around the top of the island. GARDNER IsL. (near 
Hoop Ist.) : small trees all over the island (no. 1767). Hoop 
Ist.: trees 12-18 ft. high, common on all sides of the island 
except the south, where they seem to be rather scarce, (no. 
1768). INDEFATIGABLE IsLt.: Academy Bay, common trees to 
350 ft. (no. 1769) ; north side, small trees and bushes on lava 
beds; northwest side, common trees'to 750 ft., attaining their 
largest size around 600 ft.; southeast side, common trees below 
500 ft. James Ist.: James Bay, abundant below 1000 ft.; 
