MELANTHACEA FROM THE GENETIC STANDPOINT. 159 
Raceme many-flowered ; perianth yellow, segments clawed, subcordate, 
about 5 mm. long; glands half-orbicular, the upper edge free. 
15. OCEANORUS, Small. 
OCEANORUS LEIMANTHOIDES (A. Gray), Smail. 
Amianthium leimanthoides, A. Gray, in Ann. Lyc. N.Y. iv. (1837) 125. 
Amiantanthus leimanthoides, Kunth, Enum. Pl. iv. (1848) 183. 
Zigadenus leimanthoides, A. Gray, Man. ed. 2 (1857) p. 476. 
Helonias graminea, Ell. Herb. (ex Kunth, /. c.). 
Oceanorus leimanthoides, Small, Fl. S.E. Un. St. (1903) 252, 1328. 
Long Island to Georgia and Tennessee. 
The old genus Zigadenus has been broken up into four closely related 
genera. These are Anticlea, Kunth, Enum. iv. (1843) 191; Towicoscordion, 
Rydberg, in Bull. Torr. Bot. Club, xxx. (1903) 272, and Oceanorus Small, FI. 
S.E. Un. St. (1903) 252, leaving Zigadenus itself with two species, only one 
of which is known in the wild condition. Z. glaberrimus comes close to 
Melanthium, so close that very good reasons might be adduced for including 
it in that genus. The differences between these genera are as follows :— 
Plant witha rootstock; perianth-segments each with two glands. Zigadenus. 
Plant with a bulb-like rootstock ; perianth-segments each with a single 
thick gland. Oceanorus. 
Plant with a bulb; perianth-segments each with a single gland. 
Plant poisonous, ovary wholly superior; gland obovate or semi-orbicular. 
"Toxicoscordion. 
Ovary partly inferior ; gland obcordate or notched. Anticlea. 
The habit, with a rootstock or bulb; and the number and shape of the 
glands at the base of the perianth-segments, are thus the main distinguishing 
features. It is reasonable to suppose that the gland differences at any rate 
may have originated by single steps. Anticlea and Toxicoscordion, the former 
having about 10 species in North America and two in northern Asia, and the 
latter with about 12 species in western N. America, might be regarded as 
the oldest genera. But, so far as I am aware, the bulbous condition, which 
has arisen independently in many families, has always been derived from an 
ordinary stem or a rootstock, and not vice versá. Hence we must regard the 
ancestor of Zigadenus glaberrimus as representing the original stem, from 
which in one direction Z. glaberrimus was derived, perhaps through a 
mutation in which the basal glands became divided into two, while in 
Z. (Oceanorus) leimanthoides the bulb-like development began, to be completed 
in the ancestors of Toxicoscordion and Anticlea. In the latter, meantime, the 
glands became obcordate or more or less bifurcated, and the ovary partly 
inferior. 
It is necessary to assume an extinct ancestor having a rootstock and 
a single undivided gland, Aside from this, there is no evidence of 
