276 THE AMERICAN MONTHLY [December, 



prevent the brilliancy of the colors. A great degree of moisture seems 

 also to produce early changes. During the past very wet season in New 

 England the leaves of maples in wet grounds showed bright colors as 

 early as the middle of August. A medium amount of moisture and late 

 frost seem to be favorable to the greatest brilliancy of the leaves. The 

 colors of flowers and fruits are due to similar changes in which other 

 coloring matter of a slightly different chemical composition is produced. 

 The chlorophyll of the green flower or fruit is changed into a special 

 coloring matter. This in the case of yellow flowers is anthoxanthin ; 

 of white flowers, antholeucin ; of blue flowers, anthocyanin, etc. These 

 changes are produced as the fruit matures or the flower opens. Violet 

 and purple tints are probably due to the action of acids in the cells upon 

 their coloring matters. 



The fall of the leaves is due to the peculiar structure of the leaf pet- 

 iole. A layer of rather large cells at the union of the petiole with the 

 stem of the plant is deprived of some of its nourishment whereby its 

 walls remain thin, and the protoplasm becomes at length dried or killed 

 by frost when the cells shrivel and break, and the leaf having nothing 

 to support it falls from the stem. 



Micro-photographs. 



Definition. — Micro-photographs are pictures produced by photo- 

 graphing large objects or views down to size so small as to require to 

 be examined under the microscope. Photo-micrographs, on the con- 

 trary, are pictures of very small objects made by magnification through 

 the microscope, and when thus enlarged may be examined with the 

 naked eye. Micro-photographs are small photographs — smaller than 

 the objects. Photo-micrographs are large photographs — larger than the 

 objects. 



Illustration. — It is quite common to see at soirees the Loi-d's Prayer 

 under the microscope. The micro-photograph is mounted on a slide 

 for this purpose. At the recent inauguration of President Harrison 

 boys sold thousands of watch-charms consisting of micro-photographs 

 of Harrison, Morton, and the White House, mounted in little ivory 

 telescopes. The deception was so fine that an intelligent friend — a col- 

 lege graduate — hunted the side of a room carefully over to find the pic- 

 tures on the wall towards which he had pointed the watch-charm, little 

 believing that they were contained in the T ^ inch aperture through which 

 the light had reached his eye. 



Process. — The operations of micro-photography are thus described in 

 a recent number of the English Mechanic : 



The process is simple, but it requires much practice to get good 

 effects. All you have to do is either to substitute a microscope (minus 

 the eye-piece) for the lens in the camera, or to make a little camera to 

 suit ^-plates, divided into four, as recommended by Dr. Maddox Brown, 

 and fix on a microscope instead of the eye-piece. The first method is 

 most commonly adopted. The camera is fixed on a kitchen-table, the 

 microscope is turned down to a horizontal position, the joining of the 

 eye-piece end of the microscope to the camera must be perfectly light- 

 tight. Use a large condenser to thi - ow the light of a paraffin lamp at a 

 proper angle through the object to be photographed, and through the 



