CACTACE^ OF MEXICO SAFFORD. 



541 



ously colored in tints of rose, crimson, purple, yellow, orange, or 

 copper color, and sometimes scarlet. Often they are pure white, 

 gradually becoming suffused with rose color in age. In a few 

 species they are comparatively sober tinted, and sometimes almost 

 concealed beneath the spines of the plant, and in some cases 

 they are small and inconspicuous, as in the epiphytal Rhipsalis. 

 Some are diurnal, others nocturnal; some open at sunrise and close 

 at night or when the sky is clouded; others open at a certain hour 

 and close at a certain hour of the day or night ; some last for several 

 days, some for a day, and some for only a few hours. 



The flowers of Cactacese do not possess a well-defined calyx and 

 corolla, although the outer floral leaves are often quite sepal-like and 

 the inner ones true petals. In one great division of the family, 



Fig. 7. — Opuntia flower. 



Fig. 8. — Flower of Cereus. 



which has been named Rotatiflorce^ they are widely spreading and 

 wheel shaped, as in the genus Opuntia ; in the other division, Tubuli- 

 florcB^ to which Cereus belongs, the floral leaves form a tube, often 

 remarkably long and slender, crowned with a spreading limb. The 

 floral leaves are not arranged in definite series, but form a spiral 

 in which the scale-like lower bracts gradually assume a sepal-like 

 appearance and at length become broad and petaloid. In all cases 

 the perianth crowns the ovary, and often after withering it persists 

 as a crown to the fruit. The stamens are numerous and are inserted 

 on the petals or perianth tube. The style is more robust and longer 

 than the filaments. It usually expands at the summit and bears a 

 stigma divided into several or many rays. Sometimes the stigma is 

 brightly colored and looks like a star issuing from the dense cluster 

 of anthers, adding no little to the beauty of the flower. This is 

 especially the case in certain species of Echinocereus, having the 

 bright yellow or orange-colored stamens surmounted by an emerald- 

 green, star-like stigma and surrounded by petals of rich rose purple. 



