CACALIOPSIS 



CACTUS 



609 



Nardosmia, Gray. Stout, 1-2 ft. high, loose, woolly, 

 but becoming nearly glabrous: Ivs. nearly all radical, 

 not unlike those of Petasites palmata, long-stalked, 

 5-9-cleft or very rarely parted, the lobes dentate or 

 cut: heads an inch high, in a loose cluster at the summit 

 of the nearly naked st., fragrant. Pine woods, Calif, 

 to Wash. Intro, by Gillett in 1881 as a border plant. 



CACAO, COCOA: Theobroma. 



CACTUS, CACTI. The plants correctly designated 

 by this name constitute the family Cactacese. Scarcely 

 any group in the whole vegetable kingdom is more 

 remarkable for its strange and varied forms, the beauty 

 of its flowers, and wonderful adaptation to desert life. 

 It is not, however, confined to desert regions; for in the 

 moist forests of the tropics of the New World it is 

 represented by a number of interesting forms often 

 epiphytal or scrambling in their 

 habit of growth, with beautiful 

 flowers and sometimes with 

 delicious edible fruit. 



"Botanical Features of North American Deserts," 

 publication No. 99 of the Carnegie Institution of 

 Washington, 1908. 



To the southward, the family extends to Chile and 

 Argentina. Giant torch thistles and echinocacti are 

 scattered over the pampas of Uruguay, and melon- 

 shaped echinopses amid the snows of the lofty plateau 

 of Bolivia. 



The genus Mamillaria, so well represented in the 

 southwestern United States and Mexico, is almost 

 absent from Central America, the representative genera 

 of that region as well as of the warm Huasteca region 

 of eastern Mexico being Cereus, Pereskia, Pereskiopsis, 

 Nopalea, and Opuntia; while the "turk's-head" or 

 "melon cacti" are chiefly West Indian. 



The peculiar structure of columnar, opuntioid, and 

 melon-shaped cacti is undoubtedly the result of exces- 

 sive dryness of the climates in which they occur, to 

 protect themselves from which they have been obliged 

 to store up water and to 

 reduce their transpira- 



712. Tips of Rhipsalis 



cassytha. 



713. Skeleton of 

 Opuntia stem. 



714. Pereskia aculeata. 



715. Opuntia joint with leaves. 



The Cactacese are confined to America, the only 

 apparent exception being the genus Rhipsalis, com- 

 posed of plants with the habits of the mistletoe, grow- 

 ing on the trunks and branches of trees, and bearing 

 small pellucid glutinous berries (Fig. 712). This genus, 

 endemic in tropical America, has found its way to 

 Africa, the island of Mauritius and even to Ceylon; 

 and several opuntias, or prickly pears, occur on the 

 shores of the Mediterranean, in South Africa, and Aus- 

 tralia, where they have made themselves so thoroughly 

 at home as to be regarded by many writers as 

 indigenous. The Cactaceae are not confined to trop- 

 ical or even semi-tropical regions. At 

 least two species of Opuntia extend 

 northward into British Columbia, and 

 species of Echinocereus, Echinocactus, 

 and Mamillaria are found in the state 

 of Colorado. The xerophytic forms 

 flourish especially in the southwestern 

 United States, the Mexican plateau, 

 the peninsula of Lower California, where 

 there are great cactus forests, and the 

 vicinity of Tehuacan, in the southern 

 part of the Mexican state of Puebla, a 

 region celebrated for its remarkable and 

 gigantic tree-like forms related to the 

 genus Cereus. For an account of the 

 vegetation of 'the deserts of the south- 

 western states and of Mexico, the reader 

 is referred to Frederick V. Coville's 

 "Botany of the Death Valley Expedi- 

 tion," published as Vol. IV of the 

 "Contributions from the United States 

 National Herbarium, 1893;" Coville 

 and MacDougal's "Desert Botanical 

 Laboratory of the Carnegie Institution 

 1903"; and to D. T. MacDougal's 716. Cactus spines. 



tion as low as possible. They have a more or less pro- 

 nounced woody axis surrounded by pulpy cellular tissue 

 (parenchyma) in which the water-supply is stored. The 

 stomata are usually situated in depressions or grooves 

 in the leathery cuticle; and as an additional means for 

 checking transpiration, the cell-sap is nearly always 

 mucilaginous, while in some forms latex cells are present, 

 filled with milky or gummy fluid which hardens on 

 exposure to the air and effectively heals wounds in the 

 soft fleshy plant. Certain species of Echinocactus (viz- 

 nagas) are like great barrels studded with spines and 

 filled with pulp of the consistency of watermelon rind, 

 which is sometimes made into con- 

 serves like citron (dulces de viznaga). 

 Other forms, like species of Pereskia, 

 Pereskiopsis, and arboreous opuntias 

 have hard, woody stems and branches. 

 The reticulated skeletons of certain 

 species of opuntia (Fig. 713) are manu- 

 factured into walking-sticks, legs of 

 furniture, napkin rings, and even into 

 veneering for woodwork. In Lower 

 California and some parts of South 

 America, where other vegetation is 

 lacking, the stems of columnar cerei, 

 or "cardones," are used for construct- 

 ing habitations, inclosures, and for 

 timbering mines. Columnar cacti are 

 also planted for living fences, or hedges, 

 especially the "organ cactus" (Myrtil- 

 locactus geometrizans) of tropical Mex- 

 ico. Leaves are present in nearly all 

 cacti, but in some species they are 

 mere vestiges and can scarcely be seen 

 with the naked eye. In other species 

 they are large and perfectly developed, 

 either with distinct petiole and feather 



