178 METHODS IN PLANT HISTOLOGY 



tion of a spore, or the conjugation in Rhizopus, it is necessary to ar- 

 range a motor and a gear system to operate the camera so as to make 

 exposures of individual frames at intervals of several minutes (Fig. 

 34). For this type of work the most adaptable camera is the original 

 Eastman Model A amateur motion picture camera which is a hand- 

 crank camera and does not have a spring motor. Indeed, the Bausch 

 and Lomb time-lapse mechanism is designed to be used with the East- 

 man Model A camera. 



In making movie photomicrographs, the microscope is generally 

 used in its normal vertical position. The lens of the camera is removed 

 and the camera is connected to the microscope with some sort of an 

 optical connector or double ocular. The Zeiss Company makes a 

 special optical attachment for this purpose in which most of the light 

 from the object is reflected into the camera by a silvered prism and a 

 small amount of light passes through to the inspection ocular. The 

 Bausch and Lomb Company also provides such an attachment with 

 the equipment that they sell for movie photomicrography. In the 

 absence of a special attachment any double ocular such as the dem- 

 onstration oculars used in elementary teaching may be substituted. 

 Some sort of double ocular is necessary so that it will be possible 

 to watch the action during the time that the picture is being made. 

 It will be necessary to adjust accurately the inspection ocular so 

 that the image seen through it will be in focus when the image 

 formed on the film by the other ocular is also in focus. To ac- 

 complish this adjustment, remove the film gate in the camera and 

 place a piece of onion-skin paper which is 16 mm. in width against the 

 aperture plate. If it is preferred, a piece of ground glass cut to a width 

 of 16 mm. may be used instead. Be sure to have the ground surface 

 forward. Focus the microscope very carefully on some object until a 

 sharp image is seen on the onion-skin paper or ground glass which is 

 against the aperture plate. Examine this image with a magnifying 

 lens to verify the focus. After this image is sharp, examine the object 

 through the inspection ocular and bring the inspection ocular into 

 focus by adjusting the ring or collar provided for this purpose. Be 

 very careful not to alter the position of the objective while doing this. 

 After adjusting the inspection ocular so that it is in focus, re-examine 

 the image formed in the camera to make certain that it is still in 

 focus. When both of the images are in focus, the gate may be replaced 

 in the camera and the camera threaded with film. Further focusing as 



