40 



FAMILIES OF FLOWERING PLANTS. 



They are supposed to be degenerate Aroids, and consist merely of a 

 little disc-shaped, free floating Ix'dy, rarely exceeding one-third of an 



inch in diameter, and bear- 

 ing^ on the under surface 

 a single stamen or pistil 

 and several minute root- 

 lets. There are but three 

 genera and only 25 species 

 knoAvn throughout the 

 svorld. In our staonant 

 pools and ditches Spiro- 

 dela polyrhisa, the large 

 duckweed, is often a1)und- 

 ant, coverintj the surface 

 with a carpet of green. 

 In another genus, Woljfia., 

 we tind the plant body re- 

 duced to a little grain 

 scarcely larger than a 

 pin's head. There is a 

 strong contrast in size, it 

 will be seen, between the 

 duckweed and the giant 

 Sequoia of the Californian 

 forest I 



Fig. 3.).— The large duckweed (Spirodela polyrhijza), 

 natural size. Original. 



CHAPTER Vin. 

 Order Favmosae. 



Passing orer the comparatively unimportant families Flagellaria- 

 ceae, Restionaceae. and Centrolei)idaceae, we come to the 



Famil}^ Mayacaceae. Mayaca famih'. This is represented by a 

 single genus, Mayaca., with seven species, one of which, 3[. Auhleti, 

 reaches the southern United States. It is a delicate little creeping bog 

 plant, with a habit strongly suggestive of a moss, bearing slender 

 peduncled star-shaped flowers with a perianth composed of three sepals 

 and three white or pink petals. (See Fig. 36.) 



Family Xyridaceae. Yellow-eyed Grass family. Two genera, 

 Xyris and Aholhoda^ comprising about 60 species. The plants are 



