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RECREATIONS ™M ICROSCOPE 
How to Begin the Study of Diatoms. 
BY CHARLES S. BOYER, PHILADELPHIA. 
Go to the nearest roadside ditch, 
pond or stream, preferably the slack 
water of a mill pond. Take with you 
two small bottles. Detach from the 
stems of submerged plants or from 
stones in the bed of the stream brown- 
ish masses floating in the water. Place 
these in one bottle. Pull out from the 
margin of the mill pond the stems of 
water plants, such as pickerel weed, 
and squeeze them over the other bottle, 
examine more closely you will see that 
the dark, longitudinal line in the Navic- 
ula is really a cleft known as the raphe, 
while in the Synedra there is no cleft 
at all but merely a blank line. In this 
way you will recognize at once the 
two main divisions of fresh-water 
forms, those with a raphe and those 
without. If there is neither a blank 
line nor a raphe you will probably have 
collected forms which may be Epi- 
themia, Eunotia or Nitzschia, but these 
may be studied later. You may also 
DIATOMS ARE OF VARIED BEAUTIFUL FORMS. 
See additional illustrations on page 44 of our number for August, 1919. 
preventing the admission of mud. Now 
examine, under the microscope, the ma- 
terial by dropping some of it on a slide 
and placing over it a cover glass. In 
the material from the first bottle you 
will probably notice, with a quarter- 
inch objective, a number of needle-like 
forms which may prove to be Synedra. 
In the material from the second bottle 
you will almost invariably find some 
boat-shaped forms, pointed at each end, 
called Navicula. In the needle-like 
forms, if Synedra, you will see a fine 
blank line extending the length of the 
diatom and numerous fine, transverse 
lines. In the Navicula you will see a 
blank line down the middle, together 
with a dark line interrupted in the cen- 
ter of the valve, and, probably, some 
transverse or radiating lines. If you 
notice round discs which may be 
Cyclotella or Meloseira, in which there 
is no raphe at all but the naviculoid 
forms should be studied first. If, after 
examining the living diatoms, noting 
their movements forward and back- 
ward, in the case of Navicula, and their 
peculiar, yellowish contents, called 
chromaphores, take a small quantity 
with a pipette and place on a cover 
glass. Heat the cover until it becomes 
red hot, if possible, on a thin metallic 
plate such as is used in taking tintypes, 
and, when cool, place it on a drop of 
balsam on a slide and heat it. You will 
then have mounted a slide containing 
numerous diatoms in various positions 
for study. You will notice that when 
the naviculoid form is lying at right 
angles to the usual view it will appear 
