FAMILIES OF FLOWERING PLANTS. 71 
tions to this general rule. The union of parts other than the corolla is 
also considered in classification, but everything points toward a com- 
mon end, and we can readily understand why the Compositae are now 
regarded as the very highest of the Dicotyledons, occupying a place 
similar to the orchids among the Monocotyledons. In the Compositae 
the corolla and calyx are each united. into a tube;: the stamens form 
also a tube; and lastly, the flowers themselves are aggregated into a 
head closely resembling a single flower, with a calyx-like cluster of 
bracts at its base. 
The orders which we shall discuss in this and the next few suc- 
ceeding chapters strongly remind one of the earlier orders in the 
Monocotyledons. They are mostly monoecious or dioecious plants, 
with no perianth and inconspicuous flowers frequently in dense clus- 
ters: The order Verticillatae comprises only a single family. 
Family Casuarinaceae. Casuarina Family. A most remarkable 
group of trees, the systematic relationship of which has puzzled bota- 
nists for many years. The pine-like aspect, coupled with certain pecu- 
liarities in the method by which the ovule is fertilized, indicates a 
position close to the Gymnosperms, and it has therefore been placed by 
Engler and Prantl at the beginning of the dicotyledonous series. Yet 
the plants have still more striking points of similarity in structure to 
certain cryptogams, the jointed stems immediately suggesting an 
Equisetum. There is but a single genus, Casuarina, represented in 
the tropical Indo-Malayan region by about 20 species. C. equdseti- 
jolia is: much used as a shade tree in Key West, Florida, the accom- 
panying illustration (Fig, 57) giving an excellent idea of its lofty pro- 
portions and graceful foliage. The fruit is borne in small, woody, 
pine-like cones. 
The order Piperales consists chiefly of herbs, with small flowers 
usually in close spikes; the floral envelope is wholly wanting. There 
are four families. 
Family Saururaceae. Lizard’s-tail Family. Three genera, two 
of which are North American, the third Asiatic; two of them contain 
only a single species. The plants are perennial herbs with alternate 
leaves; the flowers are borne in spikes, and are perfect, with from 6 to 
8 stamens and an ovary of several carpels. Saururus, the principal 
genus, is a familiar object in shaded swamps, its nodding spikes of 
white flowers suggesting slender tassels (See Fig. 58.) 
