1917] 
GATES—THE GENUS TRILLIUM 65 
will lead to the supplanting of the original type more quickly 
than when the step is a narrow one. 
Western Pennsylvania to Ohio and southeastern Minne- 
sota, south to Kentucky and Nebraska. 
27. T.rivale Wats. Proc. Am. Acad. 20: 378. 1885. 
This species has perhaps been derived from Т. ovatum 
through a dwarf mutation and other changes, in the same way 
that Т. nivale has probably been derived from 7. grandi- 
Лоғит. Like Т. nivale it is a dwarf, but here the resemblance 
ceases except that the leaves are petioled. It resembles Т. ova- 
twm in its recurved stigmas, but differs in every other part. 
The leaves of Т. rivale are not only very much smaller but 
they are ovate (not rhombic-ovate), rounded or subcordate at 
base (not cuneate), and petioled (not sessile). The flowers 
are much smaller, the sepals more broadly lanceolate, the 
petals subrhombic, narrowed to a claw, white but speckled 
. with purple near the сещег! In T. ovatum the petals are 
white, soon changing to rose color and dark red. The dis- 
tinctions of T. rivale are so numerous that it is not profitable 
to conjecture further concerning its origin. The extremes of 
size variation observed are as follows: stems 8-24 em. long, 
1-3 mm. thick, peduncle 6-8 em. long, leaf-blade 3-7 em. long, 
1.7-4 em. wide, petiole 6-23 mm. long, sepals 9-15 mm. long, 
9-8 mm. wide, petals 15-27 mm. long. 
In the coast mountains of northern California and southern 
Oregon. 
28. T. Catesbaei Ell. Sketch 1: 429. 1821. 
Solanum triphyllon; flore hexapetalo, carneo Catesb. Nat. 
Hist. Car. 1: 45. pl. 45. 1771. 
T. cernuum L. Өр. Pl. 339. 1753, in part. 
T. nervosum ЕП, Sketch 1: 429. 1821; Lodd. Bot. Cab. 19: 
pl. 1860. 1832. 
T. stylosum Nutt. Gen. 1: 239. 1818. 
This species and T. affine are markedly different from the 
other pedunculate species of Trillium. In them the stigmas 
1 According to Howell (Fl. N. W. Am. 1: 661. 1902), this is apparently 
present in some specimens and absent in others. 
