2o86 A TEXTBOOK OF THEORETICAL BOTANY 



flowers, mostly paired, one sessile, the other or both pedicellate; 

 borne in solitary or panicled spike-like racemes. Glumes mem- 

 branous to coriaceous, enclosing the flowers. Outer paleae 

 hyaline. Stamens three. The female spikelets are two-flowered 

 with lower flowers barren, solitary or paired, embedded in the 

 hollows of a thickened, pointed rachis or enclosed in the 

 thickened sheath or crowded in rows on a thickened rachis. 

 Outer paleae hyaline. 



The tribe contains eight genera which are tropical in origin. The most 

 important genus is Zea with the single true species Z. mais (Fig. 2022) 

 which is Maize or Indian Corn. Maize is an extremely important cereal, 

 not only of the tropics but of temperate countries, and we shall reserve our 

 discussion of it until Volume IV. The genus Coix contains six Indian and 

 Chinese species, including C. lachryma (Job's Tears). The inflorescence 

 has a broad, concave bract at the base, enclosing the single female flower. 

 The upper flowers are male. The bract forms the hard covering of the fruit, 

 which is pear-shaped. It has a grey, pearly lustre and is used for ornamenta- 

 tion. The genus is cultivated as food in Burma, and used in medicine in 

 China. 



Euchlaena mexicana, which is very similar to Maize, is used as a cereal 

 in Central America, and as a fodder in warm countries, as is also Chionachne 

 cyathopoda. This and the preceding tribe may be regarded as showing the 

 highest degree of specialization of the spikelets and of the inflorescence 

 exhibited by the Gramineae and according to Hubbard marks the chmax 

 in the evolution of the Panicoideae. 



MICROSPERMAE 



The Microspermae are monocotyledonous herbs in which the flowers 

 are highly specialized with regard to insect-pollination. Many are sapro- 

 phytic, while others live as epiphytes. The flowers are cyclic and are based 

 upon a pentacyclic trimerous system; but there is often considerable 

 reduction in the number of parts, especially of the androecium. The 

 perianth is usually composed of two trimerous whorls, the outer whorl 

 being petaloid. The ovary is inferior and composed of three carpels which 

 may form a trilocular or unilocular structure bearing many ovules. The 

 fruit is a capsule and the seeds are very minute with a thin membranous 

 testa and a very small, few-celled embryo, sometimes with a scanty endo- 

 sperm but often lacking any nutrient tissue and dependent upon an endo- 

 trophic fungus for its germination and development. 



As here treated the order contains two families, the Burmanniaceae 

 and the Orchidaceae, which are separated chiefly by the fact that in the 

 former the flowers are actinomorphic and the seeds possess endosperm, 

 while in the latter the flowers are zygomorphic and the seed contains no 

 endosperm. Hutchinson separates the families into two distinct orders 

 and splits the Burmanniaceae as defined by Pax into three families. We 



