Record. lix 



developed had it been covered by a stencil, this plate may then 

 be placed in a camera and exposed in the ordinary way, and a 

 perfect positive will develop in the bath to which it has been 

 adapted. This preliminary spoiling of the plate for develop- 

 ing a negative is a very advantageous preparation for taking 

 a positive. It shortens the time of exposure, and insures 

 that a positive shall be obtained over all parts of the plate. 

 It is not yet known how short the camera exposures may be 

 made, but the present indications are that they will be as 

 short as those now made in the taking of negative pictures. 



It is currently believed by photographers that in a positive 

 plate the object has "printed its picture" upon the plate. 

 This is an entire misconception of the process. It is true 

 that in an exposure of long duration an image shows on the 

 plate before it is placed in the bath. But this image is 

 blackest where the light has acted most. It is a negative. 

 This picture disappears in the developing bath when illu- 

 minated. The plate becomes perfectly clear. The positive 

 picture then develops, exactly as a negative would under 

 ordinary conditions. 



Mr. J. B. S. Norton presented some notes on the flora of 

 the southwestern United States. Maps were shown indicat- 

 ing the parts of this region and others not well represented 

 in herbaria, as compared with other sections of the country. 

 Among: other interesting features of the Southwest was men- 

 tioned the production of many different forms or closely 

 related species in the isolated mountains surrounded by 

 deserts. This was compared with insular conditions and 

 illustrated by the mountain forms of Euphorbia. Specimens 

 of some new species from Southwest Missouri were also 

 shown. 



Mr. Walter C. G. Kirchner, of St. Louis, and Professor 

 William Edward Andrews, of Taylorville, Illinois, were elected 

 to active membership. 



Two persons were proposed for active membership. 



