1897 THE MICROSCOPE. 73 
ipo ie ROS COPE. 
New Series, 1893. 
For Naturalists, Physicians, and Druggists, and Designed to Popularize 
Microscopy. 
Published monthly. Price $1.00 per annum. Subscriptions should end 
with the year. The old series, consisting of 12 volumes (1881-1892), ended 
with December, 1892. Sets of the old sertes cannot be furnished. All 
correspondence, exchanges, and books for notice should be addressed to the 
Microscopical Publishing Co., Washington, D. C., U.S. A. 
CHARLES W. SMILEY, A. M., EDITOR. 
eee eee SSS SS eee 
EDITORIAL. 
Growth of Diatoms.— Mr. G, C. Whipple has carried 
on a series of experiments on the culture of different kinds 
of diatoms, and finds that an abundant food-supply is not 
the only condition favorable for their rapid increase; the 
temperature, the amount of light, and other factors influ- 
encing their growth. Incommon with all other chlorophyl- 
laceous plants, diatoms will not grow in the dark, while on 
the other hand, bright sunlight kills them. The intensity 
of the light below the surface of the water being affected 
by the color of the water, diatoms are found most abundant 
in light-colored water. Different genera, however, exhibit 
differences in this respect. Melosira does not require so 
much light as Synedra. The weather hasa marked influ- 
ence on the growth of diatoms. They increase most rapid- 
ly during those seasons of the year when the water is in 
circulation throughout the vertical currents. 
During these periods not only is food most abundant 
but the vertical currents keep the diatoms near the sur- 
face, where there is light enough to stimulate their growth, 
and where there is abundance of air. Some species dis- 
play strong heliotropism moving towards the source of 
light. 
