140 Methods in Plant Histology 



magnifications higher than 100 diameters still another condenser will 

 be useful. Place it between the last-named condenser and the 

 microscope. 



With so many condensers, the heat may damage preparations: 

 so place between the last-named condenser and the one next the 

 light a cooler filled with water or a solution of alum. 



With all these accessories, an additional iris diaphragm is desir- 

 able. Place it between the middle one of the three condensers and 

 the microscope, but quite close to the middle condenser. To make 

 an efficient adjustment of all these parts requires patience, practice, 

 and judgment. 



It will save time and patience if the position of the object to be 

 photographed be marked in ink on the slide by vertical and horizontal 

 lines, or by a circle drawn around it. Even with these lines, it is none 

 too easy to get the object into the desired position on the ground 

 glass. Remove the ground glass and let the image fall on a piece 

 of white cardboard a short distance back of the camera. If the 

 curtains are pulled down, the position of the object in the field and 

 the focusing of the condensers will be comparatively easy. 



The desirability of a rigid, straight, and accurate optical bed 

 will soon be realized. If one is intending to do much photomicro- 

 graphic work, the heavy, graduated optical bed is almost a necessity. 

 However, if time is no object and patience is abundant, good photo- 

 micrographs at a magnification of over 1,000 diameters can be made 

 with no apparatus except a good camera, a good microscope, and a 

 good lamp. 



The relative positions of the various parts, as we have used them 

 in making the illustrations for this book, are indicated below : 



02 FH 



> 0) 



o g 



^ 03 Jl 



,i O H3 C FH FH 



bfl -^ bJD ^ G> 



12 S |1 .1 



<> += O vn FH FH * r-X O r-=J -t-i 



P ' d S- 3 *H SrOj <U OH ^ ' ' n '- 5 fH 



Ofl 2 -3 +-> +j> c* C c "far 



S-< 03 ^ ,> 72 773 -~ O O O .^ 



OO^^ <!fe feQO OO^ 



Some data which may be helpful will be found in the legends under 

 some of the photomicrographs. 



