512 DIOSCOREACE.E. 



found in the temperate and warm regions of America, and Asia, as well 

 as at the Cape of Good Hope. There are 6 genera, according to Lind- 

 ley, and 45 species. Examples Cycas (fig. 817), Zamia (fig. 818). 



1046. The Cycadaceous family yields much starchy matter, along 

 with mucilage. From the stems of Cycas revoluta and circinalis, a 

 kind of Sago is made. A clear insipid mucilage also exudes from 



hem, which hardens into a transparent gum resembling tragacanth. 

 Zamia pumila, and other species in the West Indies, supply an amy- 

 laceous matter which has been sold as Arrow-root. The Bread-tree 

 is a name applied by the Hottentots to various species of Encephalartos. 



CLASS II. MONOCOTYLEDONES, Juss. ENDOGEN^E, DC. ENDOGENS AND Dic- 

 TYOGENS, Lindl. AMPHIBKYA, Endl. 



1047. In this great class the plants have a cellular and vascular 

 system, the latter consisting partly of elastic spiral vessels (fig. 51). 

 The woody stem (as in Palms, fig. 115, 1) is usually more or less 

 cylindrical, simple, and unbranched. There is no true separable bark, 

 no concentric zones, and no true pith (figs. 112, 113). The wood is 

 endogenous, i.e. increases by additions, which first tend towards the 

 centre, and then curved outwards in an interlacing manner (fig. 114, 2) 

 towards the circumference, where much hard ligneous matter is de- 

 posited, so as to make the exterior the hardest part (figs. 826, 827). 

 The development of the stem usually takes place by a single central and 

 terminal bud; occasionally lateral buds are produced (fig. 115, 2), and 

 at times the stem is hollow. The leaves are parallel-veined (figs. 135, 

 173, 194), except in the subclass Dictyogens, where a kind of reticula- 

 tion is visible. The parts of the flower are arranged in a ternary man- 

 ner (fig. 538), and they are often petaloid (fig. 260), sometimes scaly or 

 glumaceous. The ovules are contained in an ovary, and are fertilized 

 by the application of the pollen to the stigma. The embryo has one 

 cotyledon (fig. 504), and the germination is endorhizal (fig. 527). 



Subclass 1. DICTYOGENS.* 



1048. Leaves reticulated, often articulated with the stem, branches 

 having the usual structure of Endogens, rhizomes or underground 

 stems having the woody matter disposed in a compact circle, or in 

 wedges containing central cellular tissue, and often showing medullary 

 processes. 



1049. Order 181. Dioscoreaccw, the Yam Tribe. (Mono-epigyn.) 

 Flowers unisexual. Perianth in 6 divisions, adherent, j . Stamens 6, 

 inserted into the base of the perianth ; anthers introrse, with longitu- 

 dinal dehiscence. $. Ovary inferior, 3-celled; ovules 1-2, anatropal; 



* ^.ixTutt, a. net, and y.ivinv, to produce. 



