2o84 A TEXTBOOK OF THEORETICAL BOTANY 



which, year by year, there arise shoots which may grow up to 15 ft., with a 

 thickness of 2 in. The inflorescence is a dense, woolly spike, the first and 

 second glumes of each spikelet being covered with long hairs. Most of the 

 cultivated forms are sterile and are usually propagated vegetatively by 

 means of short pieces of the stem, each bearing a bud. Recently, however, 

 a more vigorous series of races have been grown from seed. The sugar 

 is contained in the soft tissues of the stem (see Volume IV under Economic 

 Botany). Another very important genus is Sorghum (Fig. 2020) with fifteen 



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Fig. 2020. — Soii^hitm vulgaye var. diirra. 

 Brown dhurra or Indian Millet. Plants 

 with heads of fruits. 



tropical species, many of which have been cultivated as cereals under the 

 names of Guinea Corn, Durra, Kafir Corn, Milo, Brown Corn and Sorgo. 

 The genus Cymhopogon contains about sixty species which are characteristic 

 of the savannahs of tropical Africa. Several yield essential aromatic oils 

 such as Lemon Oil, Citronella Oil and Palma-rosa Oil which are used in 

 soaps and in perfumery. Similar oils are also produced by some species of 

 Andropogon, which includes about 180 cosmopolitan species. A. odoratus 

 is the source of Ginger Oil. The two species of Vetiveria which occur in 

 Indo-Malaya possess fragrant roots which are woven into baskets and mats, 

 while the crushed roots are also used to scent water. 



3. Maydeae. Annual or perennial herbs often with tall stems bearing 

 linear or lanceolate leaves. Spikelets (Fig. 2021) unisexual, dis- 

 similar and awnless. Sexes borne on separate inflorescences or 

 on diflerent parts of the same inflorescence with the male 

 flowers above the female. Male spikelets consisting of two 



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