90 BACTERIAL DISEASES OF PLANTS 



two big windows. One window is hardly sufficient for such a 

 room if several persons are to use it, since it is often necessary 

 to make natural size pictures and photomicrographs or lantern 

 slides at the same time. For photomicrographs I use southwest 

 light in the morning and southeast light in the afternoon, pro- 

 tecting the camera from the direct light of the sun, the south 

 window therefore must not be too close to either wall. 



The principal pieces of apparatus in our room are the camera 

 stands, two or three small tables and wall-cases, and the sink 

 and w^ashing boxes. It can be entered without passing through 

 the anti-chamber of the dark room. This is important. 



Cameras and Lenses. — Whatever results are worth the time 

 spent on them are also worth recording, therefore, from the be- 

 ginning the student who hopes to become a naturalist should be 

 taught to use the camera as freely as the microscope. If he 

 learns to do this early he will have a great advantage over such 

 as neglect it. The essentials are a light-tight bellows and a 

 lens that will give a correct and sharp image, to which has been 

 fitted a shutter allowing for measured long and short exposures. 

 Shutters, however, are not absolutely essential and the size of 

 the camera is also of minor importance, if the image is sharp 

 enough to enlarge, as it will be, provided the lens is good, and 

 the focus for the photograph is correct. If, however, the lens is 

 poor or the focus is nearly out, the picture will not stand en- 

 largement. The writer with Zeiss lenses has made pictures 

 sharp enough to stand a X 10 enlargement. The camera for 

 natural size work should have a bellows long enough to give a 

 magnification of two diameters, i.e., it should be 3 times the 

 equivalent focus of the lens. I have seen nothing better than the 

 Folmer and Schwing (Eastman Kodak Company) 6>^ by 8H 

 slightly modified Collins and Brown camera figured in Vol. I 

 of ''Bacteria in Relation to Plant Diseases" (pp. 134 and 145). 

 For a light, traveling camera provided with a tripod, the Eastman 

 Company Century Grand (4 by 5) leaves little to be desired. 

 This is much less bulky than the Folmer and Schwing 5 by 7 

 Reversible-back Graphic, which, however, is extremely compact 

 and durable, and in weight stands about midway between the 

 two already mentioned. The lenses for such cameras should be 

 the best on the market, and should be provided with the Volute 



