MELANTHACEJE FROM THE GENETIC STANDPOINT. 145 
SS. robustum is somewhat more northern and more restricted. Hence if it 
originated from S. gramineum through a mutation, its origin must have been 
relatively recent ; while the origin of Nerophyllum tena, if it was derived 
from X. asphodeloides, is more likely to have occurred before their present 
It is not necessary to assume that intermediates 
Indeed, 
wide separation in space. 
occurred and have since become extinct in the intervening region. 
I know of no faets which would justify this assumption. 
The main differences between NXerophyllum and Narthecium may be set 
forth as follows :— 
Narthecium. 
Leaves linear, those of the stem short and 
distant. 
Flowers small, greenish-yellow. 
Pedicels with a short bract at base, and 
usually bearing a small bractlet. 
Perianth-segments obscurely 5-5-nerved. 
Filaments woolly, anthers introrse. 
Style very short or none, stigma slightly 
Xerophyllum. 
Leaves narrowly linear, rough-margined, 
the upper ones shorter than the lower, 
plants larger. 
Flowers very numerous, medium-size, 
white. 
Pedicels with a long bract at base, but 
without a bractlet. 
Perianth-segments usually 5-7-nerved. 
Filaments glabrous, anthers extrorsely 
dehiscent. 
Styles 3, filiform, reflexed or recurved. 
3-lobed. 
Capsule oblong. 
Seeds many, linear, tailed at each end. 
Capsule ovoid, 3-grooved. 
Seeds 5, oblong, not appendaged or only 
minutely so. 
Though Narthecium and Xerophyllum resemble each other in foliage and 
habit, yet the differences in inflorescence and flower-strueture are numerous 
and necessitate the assumption of a considerable amount of extinction between 
these forms. It is useless to hazard a guess as to the number of mutations 
involved in the passage from one genus to the other, though there must have 
been several. Of course, one genus did not give rise to the other, but 
Nerophyllum probably came through a series of definite variations from an 
ancestor of Narthecium in which the variation producing woolly filaments 
had not yet occurred. 
6. HELONIAS, Linn. 
HELONIAS BULLATA, Linn. 
Helonias bullata, Linn. Sp. Pl. (1753) 342, and Amen. Acad. iii. (1756) 12, t. 1. f 1 
Mill. Ie. (1758) 181, t. 272; Bot. Mag. (1804) t. 747; Lam. Illustr. (1823) t. 268 ; 
Lodd. Bot. Cab. (1824) t. 961; DO. in Redouté, Lil. i. (1805) t. 13; Ann. Rep. N.J. 
State Mus. (1910), p. 540, pl. 36 (1911) ; Bartonia, iii. 1 (1910) t. 1. 
Helonias latifolia, Michx. Fl. Bor. Am. i. (1803) 212. 
Veratrum americanum, Mill. Gard. Dict. ed. 8 (1768) n. 4. 
In bogs, southern New York and northern New Jersey to Virginia, and in 
the mountains of North Carolina. Rare and local. In New York it is known 
