1917] 
GATES—THE GENUS TRILLIUM 49 
Т. unguiculatum Nutt. Trans. Am. Phil. Soe. II. 5: 154. 
1837. 
This species agrees with T. lanceolatum in its tall stems, 
which are, however, frequently stout, and incurved anthers. 
It differs in that the filaments are about half the length of 
the anthers, the leaves ovate-lanceolate, oval or suborbicular, 
and narrowed into a petiole of variable length. This last fea- 
ture suggests Т. petiolatum in which the petioles are, how- 
ever, usually much longer. This condition has perhaps orig- 
inated independently in both species through parallel muta- 
tions, an interpretation which is greatly strengthened by the 
fact that similar petioled leaves occur as a variation in 
T. grandiflorum (see page 78). 
In woods, Ohio to Minnesota, south to Mississippi and 
Arkansas. 
13. Т. petiolatum Pursh, Fl. Am. Sept. 1: 244. 1814; Hook. 
Fl. Bor. Am. 2: 180. pl. 192. 1840. 
The very short and stout stem with leaves ovate-elliptie to 
reniform, and petioles as long as, or longer than, the blades, 
characterize this remarkable species which is in many respects 
a parallel to T. grandiflorum var. variegatum. Опе feels that 
the former must have originated in connection with a muta- 
tion, as the latter obviously has done. 7. petiolatum differs 
from T. recurvatum not only in the above features but also 
in its narrowly oblanceolate petals and straight anthers with 
shorter filaments. 
Idaho, eastern Washington, and eastern Oregon. 
14. T. giganteum (Hook. & Arn.) Heller, Bull. S. Cal. 
Acad. 2: 67. 1903. 
Т. sessile var. giganteum Hook. & Arn. Bot. Beechey’s Voy. 
402. 1841. 
T. sessile var. Californicum Wats. Proc. Am. Acad. 14: 273. 
1879; Gard. & For. 3: 320. fig. 44. 1890, white form. 
T. giganteum is undoubtedly distinct from the eastern T. 
sessile, being constantly much larger in all its parts. The 
nature and cause of its gigantism is a very interesting ques- 
