Senecio precox, D. C., from Mexico. 33 
New Holland, Xazthorrhoca hastilis is peculiar ; likewise in the 
limited confines of the Pedregal Senecio precox is a prominent 
and conspicuous element of the flora, and is therefore of geo- 
graphic importance. 
Senecio precox—the tree groundsel—was first described by 
Cavanilles (1794, Icones et Descriptiones Plantarum, iii, 
23 t. 244), as Cineraria precox, and this mistake was con- 
curred with by Willdenow (Sp. Pl. v, 3 p., 2078), Sprengel 
(Syst. Veget., v, iii, p. 546,) and De Candolle (Hort. Genev., 
t. 7). De Candolle in his Prodromus (vi, p. 431) transferred 
the plant from the genus C7zzeraria to Senecio, thus correcting 
the mistake into which the Spanish priest and botanist had 
fallen. The plant is a native of Mexico, and according to 
Hemsley (Biologia Centrali-Americana ii, 246), it has been 
collected at the following places and by the following botan- 
ists: North Mexico, region of San Luis Potosi, 6,000 to 8,000 
feet (Parry and Palmer, 540); South Mexico, Valley of Mex- 
ico (Bourgeau, 178); around Toluca (Andrieux, 295); Guan- 
ajuato (Hertweg, 123); Tlalpam Pedregal (Harshberger) ; 
without known localities (Mairet, Mogino, Bates, Pringle). 
Morphology —The plant reaches, when fully matured, a 
height of three or four feet and usually stands upright with- 
without any lateral branches (Plate VII, Figs. 1 and 2). 
These, however, occasionally appear at the side and by their 
growth soon overtop the main stem, or the stem may bifurcate 
in such a manner as to present a wide, open fork (Plate VIII, 
Figs. 1and 3). The stem is cylindrical and from an inch in ordi- 
nary specimens to nearly two inches in diameter in the larger 
ones. It is fawn colored in the living state, the coloring 
being due to the smooth, corky bark which envelops it. The 
surface is marked closely by prominent crescent-shaped leaf 
scars, by large warty-looking lenticels, and by dormant buds, 
which may start into activity at any time, although they appear 
in most specimens dry and wrinkled (Plate VII, Fig. 3). The 
outline of a typical plant is broken in many cases by the 
3 
