Bamboos, or tree grasses, comprise the most diverse and certainly least-understood group of plants in the grass family. Herbaceous grasses that occur in tropical shaded forests share similar anatomical and morphological features with the bamboos, and with them make up the grass subfamily Bambusoideae. Both groups have been inadequately collected, the herbaceous bambusoid grasses primarily because the plants often appear sterile when in full flower, and the bamboos because they bloom so seldom. The bamboos of Asia have received far more attention taxonomically than those of the New World, where many new genera and species are now coming to light due to recent explorations. Numerous biological problems are presented by the Bambusoideae, such as the phenomenon of cyclic fLowering, modes of pollination, and types of sleep movements in the leaves. Also numerous cytological questions remain to be answered. Wherever man has come into contact with bamboo he has found multiple uses for it, from food in the form of new shoots, to construction and papermaking. Apart from such practical uses as these, many members of the subfamily are cultivated as ornamentals. The genera of Bambusoideae that occurs in Asia, Africa and Madagascar, and the New World are listed. BAMBOOS, OR TREE GRASSES, occur in all continents except Europe. Some of the larger members, like Dend,rocalamus giganteus Munro, have perennial culms that attain a height of 40 m and a diameter of 20 cm, while smaller ones such as Arthrostylidium sarmentosum Pilg. have culms no thicker than a pencil. The leaf blades of Arthrostylidium capillifolium Griseb. are hairlike and no wider than 3 mm, while those of Neurolepis elata (Kth.) Pilg. from the Andes may reach a length of 5 m and width of 1/2 m. Between these extremes are found bamboos of every size and form, embracing the most diverse group of plants in the grass family. Regardless of size or superficial appearance, all members possess a similar basic type of leaf anatomy that sets them apart from other grasses. A number of grasses of generally smaller stature share this same type of leaf anatomy as well as the following morphological features: rhizomatous habit, petiolate blades with tessellate venation, flowers with three or more lodicules, androecium often with six stamens. We refer to these as "herbaceous bambusoid grasses." These "herbaceous bambusoid grasses" and the "woody bambusoid grasses" (or simply bamboos) are all members of the Bambusoideae Munro, the most primitive subfamily of grasses (Calderon and Soderstrom 1973). Bamboos can be characterized as those members of the subfamily that have woody culms and complex branching, a complex and generally robust rhizome system, and infrequent flowering. Many bamboos grow in open habitats where they are windpollinated, but pollination occurs rarely since bamboos flower seldom, often only at intervals of 30 to 120 years. Like many tropical rhizomatous plants, most bamboos are tetraploids. The herbaceous bambusoid grasses, as the name suggests, have herbaceous culms, and many are diploids, and in this group both the branching and rhizome system are more simple in construction. These grasses generally grow in the understory of densely shaded tropical forests where there is no wind and where some may be pollinated by insects (Soderstrom and Calderon 1973). The intimate relationship between the two groups does not allow a clear-cut separation to be made in all cases. For example, plants of the bamboo, Arundinaria pygmaea (Miq.) A. & G., reach no more than 30 cm in height, and have slender, wiry culms. On the other hand, plants of Olyra standleyi Hitchc., an herbaceous bambusoid grass, may reach many meters in length, have tough culms, and branch profusely. Members of the Bambusoideae have an extremely wide range of distribution, with some bamboos recorded from latitudes as far north as 460 and as far south as 470, and occurring at elevations as high as 4000 m. While the great majority of bamboos is found in semi-tropical or tropical habitats, a few from such regions as Japan and China, the Himalayas, and the Andes are covered with snow part of the year. Most exacting in their requirements are the herbaceous bambusoid grasses. The vast majority of known genera and species is native to the American tropics and subtropics, occurring between Mexico and 1Our studies have been aided by grants from the National Geographic Society and the Smithsonian Research Foundation. BIOTROPICA 11(3): 161-172 1979 161 This content downloaded from 207.46.13.129 on Fri, 01 Jul 2016 05:07:51 UTC All use subject to http://about.jstor.org/terms northern Argentina, and not known to thrive above