2600 



PHOTOGRAPHY 



PHOTOSYNTHESIS 



usually made slightly less dense or "contrasty" than 

 if it is to be shown without color. A photographer's 

 retouching stand, which excludes light from the eyes 

 of the worker and reflects light through the ground- 

 glass and also through the slide to be colored, is needed. 

 Coloring is effected by means of the use of dyes and 

 stains of various characters, usually obtainable in the 

 market. The color is applied by the use of brushes of 

 varying sizes. The capable worker constantly compares 

 the result of his efforts, either with standard slides of 

 high quality or through projection upon a screen by 

 means of a small lantern. 



One reason why colored lantern-slides are so much 

 more effective than those uncolored is in their exclusion 

 of excessive light, which tends to dazzle and weary the 

 eyes of the spectator, as previously suggested. Thus, 

 a sky is blue and agreeable rather than white and 

 dazzling. 



Transparent colors must be exclusively employed, 

 inasmuch as the effect to be obtained on the screen 

 through projection is wholly that of transmitted light, 

 and not by reflection. 



The use of lantern-slides in general and of colored 

 slides in particular for educational purposes has been 

 greatly fostered by the action of several states in 

 establishing departments of visual instruction, in 

 which are grouped collections of carefully made lan- 

 tern-slides upon various subjects, frequently available 

 to residents of the particular states without other 

 charge than transportation and a responsibility for 

 damage. Pennsylvania, New York, Washington, 

 Illinois, and Kansas are known to maintain such 

 departments. 



Motion-picture photography. 



Reference has been made to the recent development 

 of motion-picture photography. Motion-pictures are 

 at present being viewed by many millions of persons 

 daily in the various centers of population in the United 

 States, but as yet little organized effort has been put 

 forth for preparing motion-pictures primarily for 

 educational purposes. Through the federal govern- 

 ment, and in the Department of the Interior, the 

 national parks are brought into notice by means of 

 motion-picture films; and it is probable that a motion- 

 picture outfit, both for the making of the exposures 

 and for the proper display of the result, wih 1 shortly 

 become an essential factor in connection with any 

 modern educational institution. Particularly in refer- 

 ence to horticulture is it probable that the motion- 

 picture will show to advantage orchard and planting 

 operations and the growing of great crops (as before 

 mentioned in connection with asparagus, for example), 

 and similarly will teach quickly and entertainingly 

 many things now less adequately presented. 



Photography in natural colors. 



Many investigators have worked on this problem, 

 but without what might be called reasonable and avail- 

 able success, until, in 1907, the Lumiere brothers, acute 

 opticians and plate manufacturers at Lyons, France, 

 painstakingly developed what is known as the auto- 

 chrome process. This process uses the known but 

 unappreciated fact that color is not an inherent prop- 

 erty of matter, but a sensation of the eye relating wholly 

 to the character of light reflected from any object. 

 Exceedingly minute particles of nearly transparent 

 starch, colored to three primary hues, are intermingled 

 and spread in a single layer over the surface of a glass 

 plate, and upon this layer there is coated a sensitive 

 and so-called panchromatic photographic emulsion. 

 These minute starch particles, averaging about 5,000,- 

 000 to the square inch, serve when the prepared plate 

 is exposed glass side to the object (contrary to the usual 

 practice) to separate or screen out the reflections from 

 the object transmitting certain intensities relating to 



the colors then expressed in that particular light. Thus, 

 from a red rose with green leaves, light is reflected 

 through these dots to the effect that the underlying 

 photographic emulsion is suitably affected for the pur- 

 pose in mind. After exposure there occurs a process 

 of development and re-development which removes 

 most of the photographic emulsion save such as marks 

 out the delineation of the object as depicted by the 

 lens, and as will serve to obscure the colors not wanted. 



Under favorable conditions, the effect is an actual 

 photograph in color upon a glass plate or transparency, 

 which must be viewed as such by transmitted light 

 suitably reflected from a white cloud or a white sur- 

 face. If the light used in reflection has a differing 

 spectrum from that used in the making of the view, 

 the colors will not be seen as they were when the 

 photograph was taken. 



As yet no means have been devised for adequately 

 duplicating these transparencies on glass, which, 

 therefore, while very beautiful when properly made and 

 viewed, serve rather as color memoranda or records 

 than for the reproductive purpose conceived of an 

 ordinary photograph. 



In this book use has been made of the autochrome 

 for obtaining the color records upon which the various 

 color plates have been produced. For example, Plate 

 VIII, Vol. I, showing the York Imperial apple, is a 

 successful reproduction of an autochrome, as also is 

 Plate XX, showing hardy bulbs in full color, and 

 Plate XXV, celery, showing current commercial prac- 

 tice in exact color. 



These autochromes are relatively expensive to make, 

 but require only a special ray-filter in addition to the 

 ordinary camera equipment. With autochrome plates 

 the careful worker is able to obtain many important 

 and delightful records. 



Inasmuch as the autochrome is viewed with success 

 only by transmitted light, it early occurred to those 

 working in this method to propose the autochrome as a 

 means of obtaining a perfectly colored lantern-slide. 

 Several collections have been made which show in an 

 exceedingly beautiful manner great scenery, portraits, 

 and the like, but the disadvantages encountered are to 

 the effect that inasmuch as the autochrome is much 

 less transparent than the average lantern-slide, it can- 

 not be shown with success in connection either with an 

 uncolored or a colored lantern-slide. If autochrome 

 lantern-slides are grouped together and shown in a 

 relatively small image with a very intense light (pref- 

 erably that of the electric arc only), the result is 

 excellent. 



Other methods said to accomplish color photography 

 spring up from time to time. So far, however, not one 

 of them has been found to be of a permanently valuable 

 and desirable character, or in any sense equal to the 

 autochrome, which in itself is rather inadequate. 



The use of photography in relation to horticultural 

 education and merchandising is merely in its infancy. 

 It is probable that greatly improved methods of re- 

 production will permit of the more extensive and more 

 effective use of photographs, and it seems certain that 

 the moving-picture will assume a much greater impor- 

 tance in educational, philanthropic, and commerical 

 practice. Acquaintance with photography is, there- 

 fore, likely to prove of increasing value to the horti- 

 culturist, j. HORACE MCFARLAND. 



PHOTOSYNTHESIS. Green plants exposed to 

 sunlight at a growing temperature are able to manu- 

 facture organic food substances, that is, carbohydrates. 

 The term photosynthesis, derived from Greek words 

 signifying "light" and "putting together," is applied to 

 this process of food manufacture. Green plants manu- 

 facture not only their own food carbohydrates but also 

 are the sources of practically all of the organic matter 

 which may eventually furnish food for both plants and 



