394 



BOTANY 



quently of large size, and extremely characteristic. They have ample leaves, 

 often very large, as in the Banana (Musa). The leaves are rolled up trumpet- 

 wise when young and have a strong midrib, from which lateral parallel veins 

 run to the margin. The leaves are usually stalked, and the leaf-base is largely 

 developed, forming a conspicuous sheath enwrapping much of the stem. There 

 is commonly an underground stem, or rhizome, from which the aerial shoots 

 are produced. These, with few excep- 

 tions, bear a terminal inflorescence which 

 ends the growth of the shoot. 



B 



FIG. 370. Pontederia cordata. A, 

 leaf and inflorescence, reduced. 

 B, single flower, showing the two 

 sets oi stamens. C, cross-section 

 of ovary, showing one fertile and 

 two sterile carpels. 



FIG. 371. Bilbergia vexillaria. 

 (After BAILEY.) 



In the " Traveller ' s-tree " (Ravenala) there is a perennial upright trunk, and 

 the inflorescences are lateral. The enlarged leaf-bases of this plant serve as 

 reservoirs of water. 



The flowers are zygomorphic, and only very rarely are all the stamens 

 developed. The ovary is inferior, and the seeds contain a small embryo, which 

 is imbedded in perisperm, or nutrient tissue developed from the nucellus of the 

 ovule. The flowers are often borne in the axils of conspicuous bracts, which 

 sometimes are very vividly colored. Some of the species of Heliconia have 

 yellow, or scarlet and yellow, bracts of great beauty, and the bracts of some 

 species of Zingiber are white or pink. 



The least specialized flowers are found in the Musacese, or Banana family. 

 Here five perfect stamens are generally present, and a rudiment of the sixth one 

 is often apparent. In the Ginger family (Zingiberacese) only one perfect sta- 

 men is developed, and one of the others is broad and petal-like, curiously resem- 

 bling the labelluin of an Orchid (Fig. 372, G). 



