76 MISSOURI BOTANICAL GARDEN. 
occurrence of tannin and a bitter principle in others; their 
protandry and exclusive adaptation to wind pollination (cf. 
Miller’s writings, and notes by Thomson in Trans. Bot. Soc. 
Edinburgh, xiv. 105, and Tulberg in Bot. Notiser, 1868, 
12); and the adaptation of the greater number of species 
to wind dissemination, by the enlargement of the inner seg- 
ments of the perianth during ripening, although some of 
those with fimbriate valves may profit by attachment to 
animals, while &. Lappula and R. hamatus form verita- 
ble burs, as Huth has shown in Bibl. Bot. 1887, No. 9, p. 
13 (Just, xv. part 1,433). Causation of sex in the dioe- 
cious £2. Acelosella is discussed by Hoffmann in Bot. Zeitung, 
xhii. Chatin describes the organogeny of the andrecium 
in Comptes Rend. vol. 78, 254 (Just, 1874, 479). Herail 
considers the anatomy of the stem, in Ann. des Sci. Nat. 7 
ser. ii. 283 and 286; and Hanstein describes the mucilage 
glands of the buds in some cases in Bot. Zeit. 1868, 699 
and 799. The occurrence of tannin in considerable 
quantities is considered by Bandelier in Verhandl. Ge- 
sellsch. f. Erdkunde zu Berlin, 1885, xii (Just, xiii. part 2, 
234); and Borscow notes the presence of chrysophanic 
acid in the roots, in Bot. Zeit. 1874 (Just, ii, 126, 834). 
Other references concerning economic products and prop- 
erties in the genus, — few species of which are of any con- 
siderable economic importance,—are given under the 
several species, particularly R. hymenosepalus, and the 
copious indexes of such pharmaceutical periodicals as the 
American Journal of Pharmacy. 
SYNOPSIS OF NORTH AMERICAN SPECIES. 
§ Acetosella. — Dioecious: inner segments of perianth without dorsal 
callosity, not reticulated, not larger than the achene: foliage acid.— 
Perennial. 
1. R. Acerosetua, L.— A span to exceptionally a foot or 
two high, tufted, propagating by creeping roots; leaves 
rarely 5 cm. long, oblanceolate, acute, the lower mostly 
