10 Contributions from the Gray Herbarium 
excelsa and V. pachycephala of Amphilepis, with V. decurrens of 
Hypargyrea, mark the closest approach to Tithonia; all three in 
fact have been included in that genus by such good authorities as 
DeCandolle and Gray. The fruiting peduncle in these two groups 
of Viguiera is however only very slightly or not at all thickened, 
while the leaves and pales, as well as the involucre, are of a different 
character, so that their separation from Tithonia is by no means 
difficult. In view of the general distribution of the two genera, the 
‘origin of Tithonia as a Central American offshoot of some lost 
Viguieroid stock related to Amphilepis is more than probable. 
The alliance of Helianthus and Viguiera has always been recog- 
nized as a close one. As was natural, the first species of Vzguzera 
which were discovered (V. dentata, V. linearis, V. quinqueradiata) 
were published as species of Helianthus by Cavanilles, and some 
later ones have been described under the same name. In general, 
the pappus of Helianthus is composed of two paleaceous and very 
eaducous awns, while that of Viguiera, of two awns and several 
intermediate squamellae, is strongly persistent, but dubious and 
more or less intermediate species are not wanting. Some four 
species of Helianthus are mentioned by Gray in the Synoptical 
Flora in which the awns of the pappus are at least occasionally ac- 
companied by squamellae, and two or three more have recently 
been added to this list by Cockerell. Most prominent of these 
species is Helianthus rigidus (Cass.) Desf., which on this account 
was at first elevated into a genus (Harpalium) by the over-analytic 
Cassini. In this species, however, as in the others which possess 
squamellae, the entire pappus is quickly deciduous, and as they 
also have the typical habit of Helianthus they must be considered 
somewhat abnormal examples of that genus still retaining traces 
of their Viguieroid ancestry. There are also in Lower California 
and adjacent California and Mexico two species more distinctly 
intermediate between the two genera, being those originally de- 
scribed as Encelia nivea Benth. and Viguiera similis Brandegee- 
The former, which was twice redescribed by Gray under Helianthus 
and once under Gymnolomia, and has recently been again described 
and well figured by Rose and Standley as Viguiera sonorae, has 
1 gst rigidum C ass. Bull. Soc. Philom. 1818. 4 (1818). Helianthus 
H. rigidus (Cass .P 
8¢ is El j 
ed. 3. 184 (1 829). A and rigida Hort. ex ‘Gardn. C rete N.S. xvi. 396, fig. 
75 (188i). For full syn. see Gray, Syn. Fl. i. pt. 2. 274 (1884). 
