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. — Abingdon Isl. : common trees to 1000 ft., 

 below 400 ft. they are small and scattered, (no. 1762). Albe- 

 marle Isl. : 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 

 Hood Isl.) : small trees all over the island (no. 1767). Hood 

 Isl. : 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 Isl. : 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 Isl. : James Bay, abundant below 1000 ft. ; 



