NYCTAGINACEÆ. 5 
Nyctaginia capitata’ has the same vegetative organs, the same 
flowers, and the same fruit as Mirabilis, but it has been made into a 
distinct genus because its flowers are united in great numbers into a 
terminal false capitulum, in an involucre formed of numerous bracts, 
and because its stamens and capitate style protrude from the perianth, 
instead of remaining included. It is a herb of Mexico and Texas. 
Okenia hypogea is à Mexican herb, the glutinous branches of 
which are prostrate on the sand, and bear terminal solitary flowers, 
in form like those of Hirabilis. But these flowers have from twelve 
to eighteen stamens, a style peltate and stigmatiferous at the apex, 
and the fruit surrounded, like that of Airabilis, by an indusium of 
similar nature, buries itself in the sand to ripen, while the peduncle 
which supports it bends and lengthens greatly. The involucre 
surrounding the enlarged portion of the perianth is here formed of 
three leaves more developed than those of <Acleisanthes, smaller 
than those of the true A/irabilis, imbricate at first, but afterwards 
caducous. 
In Pentacrophys Wright an herbaceous plant from Texas, the ter- 
minal or leaf-opposed sessile flowers are constructed almost like those 
of the preceding genera, but they have an involucre of three subulate 
bracts, a diandrous androceum, and the base of the perianth, which 
persists around the fruit, takes the form of a truncated cylinder, 
traversed lengthwise by five prominent, thick, obtuse ribs, terminated 
by a glandular swelling. The apex of the indusium presents a small 
opening into the cavity, which contains a small fruit, formed, in 
fact, like that of Hirabilis.' 
Selinocarpus has the same organs of vegetation as all the pre- 
ceding plants, and bracts and flowers like those of Acleisanthes, but 
the androceum is composed of from two to five stamens, and the five 
ribs of the indusium expand around the fruit into five vertical 
wings, or into a smaller number of those membranous expansions 
which make the fruit resemble in form certain Uxbellifere. 

1 Cnors., in Mem. Soc. Gen., xii.; Prodr., there are two sorts of flowers. In some the 
429, n. 3.— Boerhaavia capitata PAv., mss. (ex 
Crors.). 
2 ScHTEDE ex SouLrz et CiraM., in Linnea, 
v. (1830), 92.—Cuots., Prodr., 449, n. 14. 
3 A. Gray, Brief Char., 4. 
4 In this plant, as in most of the allied genera, 
perianth is quite developed; in others it is 
arrested sooner or later, and moreover the 
gynæceum is fertilised in the bud, and becomes a 
fertile fruit. 
5 A. Gray, Brief Char., 4, 
