442 BURSERACEAE 



1. AILANTHUS Desf. 



Large trees. Leaves odd-piniiatc. Flowers small, in large terminal panicles, 

 polygamous, the staminate very ill-scented. Fruit of 1 to 5 distinct oblong samaras, 

 with the compressed seed in the middle. — Species 7, Asia. (Ailanto, a Malakka 

 name, meaning Tree of Heaven.) 



1. A. altissima Swingle. Tree of Heaven. Tree 20 to 60 feet high; leaves 

 lYo to 2 feet long; leaflets broadly lanceolate, 3 to 6 inches long, with 2 to 4 teeth 

 near the base, the teeth wnth a gland beneath; samaras II/2 inches long. 



Native of China, introduced and become spontaneous, 100 to 2500 feet : Sierra 

 Nevada foothills and inner North Coast Ranges. June. 



Historical note. — The Chinese miners, immigrants in California in gold days, brought with 

 them from China seed of Ailanthus altissima, the Tree of Heaven of their temple grounds at home. 

 This seed they planted about the placer mining camps in the Sierra Nevada foothills. The species 

 spread, spontaneously in many places, and its colonies are now a feature of the foothill region, 

 especially about such old-time mining camps as Mormon Bar (Mariposa Co.), Columbia, Valley 

 Springs (Calaveras Co.), Angels Camp, San Andreas and Grass Valley. Frequently used as a 

 dooryard ornamental or shade tree it has also run wild in the Coast Eanges about Parkfield (Mon- 

 terey Co.), Berkeley, Petaluma, St. Helena, Vacaville, and Fruto (western Glenn Co.). This spe- 

 cies is, obviously, continuing to spread locally. It is, thus far, the only exotic arboreous species 

 in California which is aggressively spontaneous. In some deciduous fruit orchards, as in Pleasant 

 Valley, northwestern Solano Co., it is a pest, the seedlings and shoots, in spite of cultivation, 

 standing thickly after the manner in which Pteris aquilina displays itself on a hillslope that has 

 been cleared of the woody cover. 



Eefs. — Ailanthus altissima Swingle, Jour. Wash. Acad. Sci. 6:495 (1916). Toxicoden- 

 dron aliissimum Mill. Gard. Diet. ed. 8, no. 10 (1768). A. glandulosa Desf. Hist. Acad. Eoy. Sci. 

 Mem. Paris 1786:265, pi. 8 (1788), originally from China; Jepson, Man. 606 (1925). 



2. HOLACANTHA Gray 



Very thorny shrubs with rigid branches. Leaves reduced to small deciduous 

 scales. Flowers dioecious, glomerate on the branched thorns. Calyx 5 to 8-parted. 

 Petals 7 or 8. Staminate flowers : stamens 12 to 16, the filaments hairy at base. 

 Pistillate flowers: stamens 6 to 8, the anthers imperfect; pistils 5 to 10, lightly 

 connivent. Drupes small, dry, ovoid. — Species 1. (Greek holos, complete, and 

 akantha, thorn, all the branchlets thorn-like.) 



1. H. emorjd Gray. Crucifixion Thorn. Five to 10 feet high; fruiting clus- 

 ters very dense, 1 to 2 inches long; drupes soon dry and nut-like, 2^/2 to 3 lines long. 



Dry or rocky mesas, 500 to 2500 feet : eastern Mohave Desert; north side of the 

 Colorado Desert. East to southern Arizona. June. 



Locs. — Daggett (lava beds ne.), E. H. Greer; Ludlow, ace. Mary Beal; Lavic, Mary Beal; 

 Hayfields, Chuckwalla Mts., ace. James Bennie. These are the only known stations in California. 



Eefs. — HoLACANTHA EMORYi Gray, Mem. Am. Acad. ser. 2, 5:310 (1854), type loc. desert 

 betw. Gila Eiver and Tucson, Ariz., Thurher ; Torr. Bot. Mex. Bound. 45, t. 8 (1859) ; Jepson, 

 Man. 606 (1925). 



BURSERACEAE. Torchwood Family 



Trees or shrubs with alternate pinnate leaves. Calyx 3 to 5-lobed, persistent, 

 its base lined with a disk. Petals 3 to 5, the stamens twice as many as the petals, 

 both borne under the disk. Ovary superior, 2 to 5-celled, each cell 2-ovuled; style 1. 

 Fruit drupaceous but dry, 1 to 5-celled, indehiscent, or the epicarp splitting into 

 valves and falling away. Seed solitary. Endosperm none. — Genera 16, species 

 320, all continents, tropical or a few subtropical. 



1. BURSERA Jacq. 



Flowers polygamous. Ovary 3-celled. Fruit 3-angled, 3-valved, in ours by 

 abortion 1-celled and 1-seeded. — Species about 40, North and South America, trop- 

 ical and subtropical. (J. Burser, a botanist of the 16th century.) 



