CEREUS. The genus Cereus is very large, consisting of more than 200 species. The flowers are funnel-shaped, some being elongated and very showy, and they bloom mostly in the darkness of the night. Perhaps this night blooming accounts for the softness and brilliance of the delicate colourings. The plants are trees, shrubs or climbers, growing erect or spreading out with ribbed branches. They are the tallest and largest of the Cactaceae.

Cereus chalybaeas. Argentina. Has a columnar stem which when young is a beautiful blue but with age changes to dark green. There are 5 to 6 ribs with prominent areoles, furnished with brownish wool. All the spines are straight and black, the radials numbering 7 to 9, centrals 3 to 4. A very popular species, and deservedly so.

Cereus azureus. N. Argentina and S. Brazil. The stem is erect with 6 or 7 ribs, obtuse, swollen, and slightly gibbous at the areoles. Spines number 8 to 16, and are black and awl-shaped, with 2 to 4 central spines which are slightly longer. The furrows between the ribs are deep and narrow. This species is a quick grower.

Cereus jamacaru. S. America. This is a very popular species with amateurs, and is easily grown. The stem is columnar, with 4 to 6 ribs, bluish-green when young but becoming dull green. The large greyish areoles bear numerous yellow spines of various lengths.

Cereus alacriportanus. Uruguay, Paraguay and S. Brazil. Has a bluish-green stem which later becomes deep green. The areoles are whitish and rather small, and bear 6 to 9 awl-shaped spines.

Cereus peruvianus. SW. Brazil and N. Argentina. A popular favourite, easy to cultivate in a rich calcareous soil. It has 5 to 8 ribs, thick and obtuse and slightly notched, with acute furrows between. The round, brownish areoles bear about 7 radial and 1 central spines the spines in the upper areoles being often more numerous.

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