314 
COMMIPHORA 
medicine and as a -component of incense, &c. C. opobalsamum Engl, 
is said to yield the pesin known as Balm of Gilead. Other sp. yield 
Bdellium and other resins. 
Comparettia Poepp. et Endl. Orchidaceae (28). 4 sp. trop. Am. 
Compositae. Dicotyledons (Sympet. Campanulatae). The largest order 
of flowering plants, comprising about 810 genera, with over noco sp. 
— more than 10% of the total number of sp. of Phanerogams. They 
are distributed over the greater part of the earth. Although so large 
an order, the C. are well marked in their characters and cannot be 
confounded with any other order, though they have a superficial 
likeness to Dipsaceae and Calyceraceae. [For a genealogical tree of 
the sympetalous orders with inferior ovary, and their relationships to 
Umbelliferae, &c., see Hock in Bot. CentralbL 51, 1892, p. 233, and 
art. Scimbucus.\ 
Living as they do in almost every conceivable situation, the C. 
present great variety in vegetative habit, often within the boundary 
of a single genus. Of this, Senecio (q.v.) is a noteworthy example. 
Water and marsh plants and climbers are rare in the order, and so 
also are epiphytes. This latter is an interesting point, for the distri- 
bution mechanism of these plants is admirably suited to an epiphytic 
existence, and xerophily is not uncommon in the order (see p. 174). 
Another feature of interest is that the enormous majority of this most 
successful order are herbaceous plants; trees and shrubs are com- 
paratively rare. It is worthy of note that the latter form an important 
feature in the Composite flora of oceanic islands, the reason for which 
is not very obvious (see Wallace’s Island Life). 
The leaves are usually alt., frequently radical, opp. in Heliantheae, 
whorled in a few cases, e.g. Zinnia verticillata. Stipules are rarely 
present. The root is usually a tap-root, sometimes tuberous as 
in Dahlia, &c., often thickened like that of a carrot, e.g. Taraxacum, 
Cichorium, &c. For further details of vegetative organs reference 
must be made to individual genera; e.g. Aster, Barnadesia, Beilis, 
Bidens, Cichorium, Dahlia, Espeletia, Gnaphalium, Helianthus, 
Helichrysum, Lactuca, Mutisia, Petasites, Senecio, Silphium, Ta- 
raxacum. &c. 
All the tribes with the exception of xn and xm contain oil- 
passages in the root, stem, &c. In xm (Cichorieae), laticiferous 
vessels are present, commonly containing a milky white latex (e.g. 
lettuce, dandelion). 
The infl. is of racemose type, the firs, being arranged in heads 
(capita la), or rarely in spikes. These heads are again arranged in 
many cases into larger infls. — racemes, corymbs, &c., or even into 
compound heads (Echinops, &c.). In this last case, however, the 
smaller heads contain only one fir. each. The head is surrounded by 
an involucre of bracts, usually green, which performs for all the firs, 
of the head the functions that in most plants are performed by the 
