338 FRESH WATER SKETCHES. 
scribe the various interesting submerged plants which will natu- 
rally attract the attention. The beautiful feathery Myriophyllum 
and Naias, the interesting Ceratophyllum, the submerged leaves of 
the white and yellow Ranunculus (N. aquatilis and N. Purshii) re- 
duced to a mass of branching vessels, with a mere trace of paren- 
chyma; the various species of Potamogeton, the Hippuris, etc., 
etc., will all prove of great interest to the botanical student, but — 
we will at present attend to those plants only which afford good 
views of the motion of the sap. 
Among the best plants for studying this circulation are those of 
the Chara family, a group of plants formerly included among the 
Algze, but now regarded as occupying a separate and somewhat ' 
higher position. _They are very common in ponds, streams and 
ditches in all parts of our country, and may easily be recognized 
by their leafless stems and branches composed of long joints 
which are scarcely larger around than a common knitting-needle. 
Each of these joints is a single cell, within the walls of which are 
seen minute green particles, arranged in parallel: lines, which go 
obliquely around the joint, leaving at one place a narrow colorless 
band. It does not need a very high magnifying power to see in 
these tubes a most beautiful display of the phenomena of circula- 
tion. The fluid may be seen 
‘in fluent dan 
and lively PiE ETETE mounting” 
along one side of the colorless band, and proceeding along the 
whole length of the joint until it reaches the extremity, where it 
turns down on the other side of. the same band. The large starch 
globules and other masses which are borne along by the current, 
enable us to follow its course and even to measure its velocity. 
A very full account of the observations made on the circulation 
in Chara and Nitella, by Amici, Slack, Varley, Dutrochet and oth- 
ers, will be found in Hassal’s Fresh Water Algæ. p. 78. These 
plants may be kept in glass vases without any trouble and will 
prove of great interest to the microscopist not only for the phe- 
nomena of circulation but also for the curious structure of their or- 
gans of reproduction. These organs are known by the name of the 
nucule and the granule, the former being considered by some au- 
thors as the female and the latter as the male flower. The nucule 
consists of a globular body surrounded by fine spirally-twisted 
