CACTUS FAMILY 143 



Family 102. CACTACEAE.* 

 Cactus Family. 



Perennial succulent woody or herbaceous plants with globose, cylindrical, colum- 

 nar, or flattened stems, these ribbed, smooth, tuberculate, bearing broad, fleshy 

 leaves, or in ours, leafless or with small, caducous subulate leaves in Opuntia. Are- 

 oles complex, bearing wool, glochids (barbed spicules), spines, branches, or flowers, 

 or various combinations of these structures. Flowers perfect or incompletely uni- 

 sexual, sessile, solitary in an areole, but clustered when borne by contiguous areoles. 

 Perianth-segments numerous, grading from sepals to petals, imbricated, the bases 

 coalescent to form cup or tube borne at the apex of the ovary. Stamens numerous, 

 inserted on the throat of the tube. Style 1 ; stigma-lobes 1 to numerous. Ovary 

 inferior, 1 -celled, many-ovulate. Fruit a dry or fleshy berry, many-seeded. 



A family of about 120 genera and 1,200 species, native to North, Central, and South America, reaching 

 their finest development in the drier regions of Mexico. Introduced and thoroughly established in Australia. 

 Cultivated extensively as ornamentals in Europe and the United States. 



Areoles containing glochids; leaves small, caducous; flowers rotate, definite perianth-tube lacking. 



1. Opuntia. 



Areoles without glochids; leaves on vegetative parts wanting; flowers with definite, though often short perianth- 

 tubes. 

 Stems ribbed; fruits scaly or spiny, or both, often laniferous (except Pediocactus). 



Flowers borne laterally, immediately above mature spine-bearing areoles; fruit more or less spiniferous; 

 dehiscing irregularly. 

 Stems erect, 4—16 ra. tall; flowers creamy white; fruit sparingly spinose. 2. Carnegiea. 



Stems erect or decumbent, 1.5 m. tall or less; flowers not white. 



Fruit quite spiny. 



Stems 0.5-1.5 m. tall, branching near the base but not crowded-cespitose; flowers yellow. 



3. Bergerocacti'.s. 



Stems 1-3 dm. long, cespitose; flowers red to purple. 4. Echinocereus. 



Fruit naked. 9. Pediocactus. 



Flowers borne subterminally above young areoles; fruit scaly (except Pediocactus), but not spiny, 

 usually dehiscing by a basal or terminal pore (except Pediocactus). 

 Fruit ovoid to oblong, scaly. 



Ribs continuous, not markedly undulate-tuberculate; principal spines annulate, some of them 

 flattened. 

 Axils of scales on fruit copiously and persistently woolly; fruit dehiscing by a terminal 

 pore; plants cespitose. 5. Echinocactus. 



Axils of scales on fruit naked; fruit dehiscing by a basal pore; plants usually solitary. 



6. Ferocactus. 



Ribs distinctly undulate-tuberculate; principal spines terete, not markedly annulate. 



Axils of scales on fruit naked; spines straight, not hooked; seeds muricate, hilum ventral. 



7. Echinotnastus. 



Axils of scales on fruit woolly; some of central spines hooked; seeds tuberculate, hilum 

 lateral. 8. Sclerocactus. 



Fruit globose, smooth, scaleless or essentially so; dehiscing irregularly down the side. 



9. Pediocactus. 



Stems bearing spirally arranged tubercles; fruits smooth, scaleless, berries with no definite dehiscence. 



Tubercles distinctly narrowly grooved on the upper side; fruit greenish when mature. 



10. Coryphantha. 



Tubercles not grooved; fruit red when mature. 



Seeds rugose, with a large corky aril half as large as body of the seed. 11. Phellosperma. 



Seeds favose-reticulate or pitted, no aril present. 12. Mammillarta. 



1. OPUNTIA [Tourn.] Mill. Card. Diet. abr. ed. 4. 1754. 



Fleshy cacti with more or less woody skeletons and jointed cylindrical, clavate, or 

 flattened stems and branches. Roots fibrous or fleshy-tuberous. Areoles axillary, bearmg 

 short, readily detached barbed bristles or glochids and usually 1 to several stout spines. 

 Spines naked or ensheathed in dry, papery coverings. Leaves usually small and terete, 

 early deciduous. Flowers borne in areoles of year-old growth ; perianth-tube cup-shaped, 

 short. Ovary areolate, 1 -celled, many-ovulate. Sepals green, grading into colored petals. 

 Stamens numerous, shorter than the petals, sensitive. Stigma-lobes short. Fruit fleshy 



* Text contributed by Ira Loren Wig/gins except for text of the genus Opuntia which is contributed jointly 

 with Carl Brandt Wolf. 



