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 Verticil latae 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 

 Eqidsetum. There is but a single genus, Casuarina, represented in 

 the tropical Indo-Malayan region l)y about 20 species. C. equiseti- 

 folia 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 w^anting. 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.) 



