In other words, individual plants are grouped in species, species into genera, genera into families, and families into orders. These orders are themselves grouped into still larger divisions; there are, for instance, twelve orders comprising all the monocotyledons, and about twenty orders comprising all the dicotyledons. Once we have decided that any plant is a monocotyledon or a dicotyledon, our next step should be as to which order it belongs, then its family, its genus, and finally its species. Needless to say, such studies are necessarily of a technical nature, and while the details of them lie outside the scope of this book, the general plan or scheme of flowering plant classification is as we have outlined it above. This scheme of plant classification has been developed not only for our convenience in sorting plants into definite categories, but more important still to show, if possible, the relationships, and particularly the development from the simplest to the most complex types of plant life. Thus the monocotyledons begin with the cat-tails, which have mere bristles for calyx and corolla, and lead by infinite gradations to the showy and highly complex orchids, which are considered the climax of the monocotyledonous families. While no general account of the plant families can be attempted here, some of the more interesting in both the monocotyledonous and dicotyledonous groups will be briefly discussed. SOME MONOCOTYLEDONOUS PLANT FAMILIES Of the simple plants of this group the Grass Family, or _Poaceæ_ (Figure 86), is the most important, for in it are all our turf grasses, the bamboo and sugar cane, besides scores of others. Over 4,500 species are known, and they inhabit every region of the globe. The steppes of Russia and our Great Plains are predominately grassy; in the wonderful bamboo forests in the tropics are also woody representatives of this family. Certain kinds in the tropics grow as vines, with great hooked spines at the joints, so that nearly every kind of growth-form is to be found in the _Poaceæ_. All agree in having very small flowers, arranged in tiny spikelets, which are themselves grouped in various ways, although the inflorescence is usually some form of spike, or raceme or panicle. The individual flowers are between chaffy scales, of which several make up each spike. Always the lowest two scales are empty, and the flowers begin in the third from the bottom, or [Illustration: FIG. 86.--BLUE-JOINT GRASS (_Calamagrostis canadensis_) FIG. 87.--WOOL GRASS (_Scirpus Cyperinus_) Fig. 86. Blue-joint grass, a common grass of North America and a member of the _Poaceæ_. Fig. 87. Wool-grass, a tall swamp sedge popularly but incorrectly spoken of as grass. It is a member of the _Cyperaceæ_ or Sedge family, which have usually triangular solid stems, whereas grasses have hollow round stems.]