the distance for the foreground, and the focus is made upon the center. After focusing, the shutter is closed, the indicator set at the time desired, and the diaphragm “stopped down” as far as possible. Plate-holder 1 is slipped into place, care being taken not to move the camera by a sudden jar. The camera cloth is dropped above the holder and allowed to hang down over the slide end. The slide is drawn and put on top of the instrument, the black edge always up. The exposure is made and the slide replaced _with the black edge outward_. This point should receive the most critical attention, as a blunder here will often cause the loss of two negatives. The plate-holder is returned to the receptacle, or merely placed in the back of the camera, which is then closed. The number of the plate, the name of the view or object, the condition of the light, the length of exposure, and the aperture of the diaphragm, as well as the date, are recorded in a notebook for this purpose. The shutter is then opened at “time,” the diaphragm thrown wide open, and the front of the camera closed. When distances are short, the camera is often carried upon the tripod. As a rule, however, it is usually removed, and the tripod folded. In making subsequent pictures, the plates should always be used in their numerical order. =240. The time of exposure= is obviously the most critical task in the manipulation of a camera. The time necessary for a proper exposure varies with the season, the hour, the condition of the sky, the light intensity of the formation, the color and size of the area to be photographed, and, finally, of course, with the aperture of the diaphragm. Fortunately for the ecologist, the variation in light intensity during the season, and even during the greater part of the day, is not great, and can ordinarily be ignored. The beginner will make the most progress by determining the exposure demanded by his instrument for taking a general view in full sunlight and with the smallest stop of the diaphragm. In standard cameras with lenses of ordinary rapidity, this is usually about one second. This will serve as a basis from which all other exposures may be reckoned until one has worked through a wide range of conditions and can recall just what time each view requires. On completely cloudy days the time required is five to ten times that necessary on a clear day; filmy clouds and haze necessitate an exposure of two or three seconds. The more open forest formations demand an exposure of about five to ten seconds on a sunny day, while the deeper ones require two or three times as long. A close view requires more time than a distant one, since the light-reflecting surface is much smaller. Quadrats require two or three seconds, and individual groups frequently take a longer time. The color of the vegetation plays an important part also: a dark green spruce forest requires twice as long an exposure as the aspen forest, and a grassland quadrat takes more time than one