16 



FAMILIES OF FLOWERING PLANTS. 



they appeared on the earth's surface in advance of the Dicotyledons. 

 The three Monocotyledonous orders which will be discussed in this 



paper consist entirely of aquatic or marsh plants, most of them with 



inconspicuous flowers and little or no 

 economic value. (See Fig. 12.) The 

 Pandanales are herbs, shrubs or 

 trees, their flowers with a perianth 

 composed merely of bristles or chall'y 

 scales. The Ilelobiae (so named in 

 allusion to their marsh loving pro- 

 pensities) are all herbs, with a fleshy 

 green or corolla like perianth; while 

 the Triuridales, comprising a single 

 family, consist mostly of saprophytic 

 herbs, or plants deriving their sul)- 

 sistence from decayino- veoetable 



Fig. 11.— Section of box-elder twig show- ' . 



ing the annual rings of growth, the vascular matter, and thus wholly destitute of 



From ''oulter's " Plant Relation.s." 



Coiiyri<rh-, l><ii:i. \i\ I >. .Xppletnn .'; Co. 



region (w) the pith rays (m) anrt the cortex 

 (c). 



leaves. 



Fig. 12.— Zones of aquatic vegetation. In the center pond lilies: at the edge smart- 

 weed: farther back cat-tails, blue flags, sweet flags and sedgt!s: still farther back soft 

 turf with grass, moss, sedges and milkweed. (From MacMillan's Minnesota Plant Life, by 

 courte.sy of the author. 



