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or sixes, 5-6 mm. long, not decayed at the tips. Often monoe- 
cious, the flowers. consisting of a single stamen or a single pistil ; 
sometimes all the flowers in the axils of the whorls staminate. 
Stamens as long as the ripe fruit; filaments thick: anthers 
large. Fruit almost oval, minutely granulated, a little over 1 
mm, in length ; the persistent style shorter than the nutlet. 
Turfy places in Siberia, Alaska and the Selkirk Mountains, 
British. Columbia (Macoun). 
2. Callitriche. L. Sp. Pl. 969. (1753). 
Widely dispersed over the earth in warm and temperate cli- 
mates. As usually reckoned, it numbers about twenty species, 
one half of them occurring in the United States. In some cases, 
however, the species run so close to each other that they can be 
distinguished only by fruit markings. In this paper Hegelmaier’s 
classification of our North American forms is retained more for 
the sake of avoiding the creation of new synonyms than for any 
other reason. A stricter grouping would probably throw C. verna, 
C. stenocarpa, and C. Bolanderi into one. It is doubtful, too, if 
C. verna and C. heterophylla should be considered as distinct 
species, since they can be separated only by the fruit, and are 
constantly confounded. Each of them, also, varies more or less 
in the shape of the fruit, so that it is not always easy to place the 
specimens. 
The leaves of most or all the species are covered on 
both sides with dark, colored dots termed by Engelman 
“stellate scales,’ and by Hegelmaier “ stellate hairs,’ Under 
the microscope they appear to be composed of a dark ring in 
which is a slightly sunken disc with a minute cell in the centre 
from which radiate lines dividing the disc into several cells. 
They are more numerous in the aquatic than in the terrestrial 
species, in the former usually having four cell divisions, and 
in the latter eight, or sometimes split into twice as’ many 
divisions. 
Authors have generally regarded the flowers as monoecious, 
calling the stamens and pistils separate flowers, although they 
may stand side by side in the same axil and enclosed in the same 
perigonium. In respect to this I am bound to say that I agree 
