28 Contributions from the Gray Herbarium 
base and short or long slender herbaceous tip, the whole so strongly 
suggestive of the Mexican series Dentatae that for a time I was in- 
clined to place at least V. australis in that group. A more careful 
comparative study of the species, however, has shown that its 
resemblance to the Dentatae is more apparent than real. Finally, 4 
4 
; 

in V. tucwmanensis, V. discoidea, and V. atacamensis (t. 2. £. 25) 
there is a distinct differentiation of the phyllary into indurated 
base and herbaceous apex which differs only in degree from that : 
met with in the Bracteatae. 5 
In the species among the Bracteatae (t. 2. f. 27-31) which appear | 
to be the most primitive, such as V. arenaria and V. radula, there 
is evident a strong differentiation in the phyllary into a very | 
strongly indurated and ribbed base and an abruptly delimited 
herbaceous apex. In such species as V. bracteata (t. 2. f. 31), V- | 
imbricata, and V. oblongifolia (t. 2. f. 28) the herbaceous tip beim 
comes less distinct and the whole phyllary broadens, until in Vi 3 
robusta (t. 2. f. 29) and V. macrocalyx the broad and blunt phylla- : 
ries are more or less indurated and vittate nearly or quite to the — : 
; 

apex, and the herbaceous tip is obscure or almost wanting. 
Closely simulating the Bracteatae in involucral characters, the 
Mexican section Leighia (t. 2. f. 33) exhibits the most highly dif- | 
ferentiated phyllaries of the genus, as well as a progressive VaTla- 
tion closely analogous to that just described for the Bracteatae. in a 
V. linearis (t. 2. f. 33) the only common and wide-spread species, 
the phyllaries of the strongly graduated involucre are sharply die : 
vided into an indurated pallid base and a short herbaceous tip, the 
latter varying from lanceolate and acute to deltoid and obtusish- — 
Through a reduction in height and thickness of the terminal ber- : 
baceous appendage, and extension through it to its tip of the vittae — 
of the main body of the phyllary, particularly noticeable in the 3 
forma latiorifolia, an easy passage is afforded to V. purisimae, 2 
which the herbaceous apex of V. linearis is represented merely by 
a darker coloration and somewhat thinner texture; to V. o 
in which the extreme tip is thin, subscarious, and scarcely nerved; 
and to V. Goldmanii, in which it is thin and scarious and nearly 0 
quite veinless, the whole involucre in fact, in the last species, bel 
very similar to that of the genus Calea. | 
The section Trichophylla (t. 2. f. 32) of Paraguay and Brazil has 
a several-seriate graduated involucre of lanceolate attenuate more ‘ 












