Composite—Dahha. 239 
has been observed in all the varieties raised. Perhaps chemistry 
may some day tell us why. 
The culture of the Dahlia has probably been carried to 
higher perfection in England than in any other country, for 
almost without exception the varieties grown are of English 
raising. Besides the old tall race, a new one of dwarfer stature 
and another bearing smaller flowers have sprung into existence. 
The varieties of the different classes range from 1 to 6 feet 
or more in height, and the flowers, or more properly flower- 
heads, from 2 to 5 inches in diameter. The comparatively 
recent Bouquet or Pompon Dahlias furnish the best varieties 
for a small garden. In some of these the florets are beautifully 
fringed, as in the pure white variety Guiding Star. For de- 
tailed information respecting the numerous varieties we must 
refer the reader to the catalogues of our great Dahlia growers. 
In addition to the above species there are two or three 
others occasionally seen, including D. coccinea (fig. 127), a 
rather taller plant with large scarlet sometimes semi-double 
flowers; and D. impericlis, of recent introduction, and better 
adapted for a large conservatory than the open air. The latter 
attains a height of 8 to 12 feet, bearing numerous smaller bell- 
shaped heads of pure white flowers, with a crimson spot at the 
base of each floret. 
Trips IV.—SENECIONIDES. 
Leaves variable. Style cylindrical, with linear awns usually 
fringed at the point, often truncate, or extended beyond the 
fringe in a cone or other appendage. 
14. SILPHIUM. 
A small genus of herbaceous plants of rather large stature, 
having opposite whorled or alternate leaves and large yellow 
moneecious flower-heads. Ray-florets female, and disk-florets 
barren. Achenes large, flat, winged longitudinally, the latter 
sometimes toothed at the top, and representing the pappus. 
Natives of North America. 
1. S. lacinidtum (fig. 128). Compass Plant or Rosin-Weed. 
—The slender stems of this species rise to a height of 3 to 6 
feet, surmounted by large flower-heads, yellow with a dark 
centre. It received the name of Compass Plant because it was 
supposed that the leaves invariably presented their surfaces 
due north and south; and the second trivial name was given 
