194 THE FORMATION 
objects should always be taken, never the shaded one. The exposures in- 
dicated above are based upon the.smallest stop. The reasons for using this 
whenever possible have already been given. When a larger stop is necessary, 
the exposure is decreased to correspond; for example, a quadrat that takes 
three to four seconds at 256 can be taken at 64 in one second. As a rule, 
_the sun should not be in front of the camera, but,.when necessary, views can 
be made in this position if the sun is prevented from shining directly into 
the lens. 
241. Developing is as important as exposing. Indeed, it may well be 
considered more important, since a properly exposed plate may be spoiled in 
developing, while an under-exposure or over-exposure may be saved. 
Owing to the ease with which plants move in the wind, the ecologist is 
obliged to reconcile himself to many under-exposures, which can be con- 
verted into good negatives only by skilful developing. Every base station 
should have a good dark room, equipped with running water when possible, 
a good ruby lantern, and the proper trays and chemicals. Prepared develop- 
ing solutions are alluring because of their convenience, but after an extended 
trial of several kinds, the writer has reached the conviction that pyrogallic 
acid, or “pyro,” is by far the most satisfactory in working with vegetation. 
Of almost innumerable formulae, the following gives excellent satisfaction 
and is convenient to use. , 
I, II. 
500 cc. water 500 cc. water 
30 grams sodium sulphite 5 grams pyrogallic acid 
30 grams sodium carbonate 
For developing, equal parts of I and II are mixed, and a few drops of a 
10 per cent solution of potassium bromide added, unless there is reason 
to suspect that the plate has been seriously underexposed. The fixing 
bath is a concentrated solution of sodium hyposulphite, “hypo,” to which 
a few drops of acetic acid are added. It should be replaced every week or 
two, depending upon how much it is used. A tray of water is kept at hand 
for bringing out the detail in underexposed negatives, and a second tray 
‘is used for washing. The “pyro” and the bromide solution should always. 
be within reach, the former for accelerating, and the latter for retarding 
the development of unsatisfactory plates. 
The image will begin to show on a properly exposed plate within one 
to three minutes after it has been put in the developer. If the image 
appears almost instantly, and then recedes quickly, the plate is badly over- 
