40 FAMILIES OF FLOWERING PLANTS. 
They are supposed to be degenerate Aroids, and consist merely of a 
little disc-shaped, free-floating body, 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: 
known throughout the 
world. In our stagnant 
pools and ditches Spéro- 
dela polyrhiza, the large 
duckweed, is often abund- 
ant, covering the surface 
with a carpet of green. 
In another genus, Wolfia, 
we find 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 
Fic. 35.—The large duckweed (Spirodela polyrhyza), duckweed and the giant 
natural size. Original. Sequoia of the Californian 
forest! 
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CHAPTER VIII. 
Order Farinosae. 
Passing over the comparatively unimportant families Flagellaria- 
ceae, Restionaceae, and Centrolepidaceae, we come to the 
Family Mayacaceae. Mayaca family. This is represented by a 
single genus, M/ayaca, with seven species, one of which, J/. Avd/et’, 
reaches the southern United States. It is a delicate little creeping hog 
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, 
Ayris and Aboltoda, comprising about 60 species, The plants are 
