352 
at which the number is reckoned. This will account for the dis- 
crepancy which occurs in the statements of different observers. The 
large roots are spongy or often conspicuously nodose for their 
whole length. With three of the genera we have no concern, as 
two of them, Philodice and Tonina, both together numbering five 
species, are restricted to tropical South America, and the other, 
Mesanthemum, numbering three species, is endemic in tropical 
Africa. 
The North American genera may be briefly distinguished as 
follows : 
Segments of the perianth four or six. 
Stamens separate. Anthers two-celled. Stamens as many as 
the perianth segments. 1. Eriocaulon. 
Stamens one-half as many as the perianth segments. 
2. Dupatya. 
Perianth of three segments. Stamens three, monadelphous below. 
Anthers one-celled. 3. Lachnocaulon. 
Ertocauton is the most extensively diffused genus, being found 
in tropical and subtropical regions throughout the world. As 
classified by K6érnicke in his monograph the species are divided 
into fourteen sections. All the species occurring within the bor- 
ders of the United States, so far as known, are acaulescent or 
nearly so, the heads single on erect peduncles or scapes, the peri- 
anth with one exception four-parted and the stamens four; the 
Mexican species are the same except in having six-parted flowers 
and six stamens. The perianth segments, at least the upper ones, 
are usually spotted with a minute black gland near the centre or 
the apex. The heads are generally quite villose and grayish in 
appearance, the parts of the perianth being strongly bearded. The 
flowers are each subtended by a bract quite similar in markings 
and general appearance to the perianth segments. Seeds oval, 
brown when mature and, under the lens, covered with blunt or 
spiny protuberances. 
As the perianth segments are in two series and often separated 
at a considerable distance, there is much variation in the language 
applied to them by botanists. K6rnicke calls the floral envelopes 
a double perigonium, the exterior calyculate and interior sub- 
corolline. Kunth speaks of them as a double calyx, while others 
