152 
METHODS IN PLANT HISTOLOGY 
After a little practice the student will read with profit the more 
extended works on this subject, among which are the following: 
The A, B, C of Photomicrography , by W. H. Walmsley (Tennant & 
Ward, New York); Photomicrography , edited by J. Spitta (Scientific 
Press, London, England); Lehrbuch der Microphotographie , by Dr. 
Richard Neuhaus (Harold Bruhn, Brunswick, Germany). 
LANTERN SLIDES 
Lantern slides are now so universally used in the lecture-room 
that every teacher should be able to make them. Three general 
classes of lantern slides, as far as the technic of making them is 
concerned, will be described: (1) lantern slides by contact, (2) by 
reducing or enlarging, and (3) by copying illustrations. 
1. Lantern Slides by Contact.—This method is very simple. 
Imagine that the lantern-slide plate is a piece of printing-out paper, 
and proceed just as in making a print on paper. Remember that 
dust on the negative or plate causes spots in the print, and that spots 
so small as to be almost unnoticeable in an ordinary print will be 
greatly magnified when they appear on the screen. Brush both 
negative and plate very gently with a soft clean brush before making 
the print. If the negative is 3jX4| inches, it can be placed in a 
printing frame of that size, and the lantern slide placed upon it with 
the two films in contact, just as in printing paper. If there is no 
small printing frame, use a 4X5, a 5X7, or even an 8X10 frame. 
In such cases, put in a piece of clean glass free from scratches or 
bubbles, and lay the negative upon it. Lantern slides may be 
printed from a portion of a 4X5 or some larger negative by simply 
placing the lantern-slide plate over the desired spot. Take great 
care not to scratch the negative. 
A much more satisfactory method is to use a box 10 inches 
square and 16 inches high, inside measurement. The box should be 
painted white inside, and the top should be a strong piece of glass; 
but there should be also a wooden lid, hinged at the back and covered 
inside with some thick, soft cloth. Inside the box, about 4 inches 
from the bottom, place two electric bulbs, one red and the other 
white. To diffuse and tone down the light, a piece of glass, ground 
on one side should be placed a little more than halfway between the 
light and the glass top. If the light is still too strong, place a piece 
of white paper above the ground glass. It is most convenient to 
