RF. CORDS. 



by some one not entirely familiar with the subject, it not infrequently happens that 

 the statements in the paper which have been omitted from the abstract as unim- 

 portant prove in the end to be the essential ones so far as the owner of the abstract 

 is concerned. For this reason, when they are within reach, the writer prefers to 

 consult the original papers and to save for original work the time consumed in 

 making long abstracts. When they are rare, frequently needed, and only to be had 



by borrowing, the writer has sometimes 

 photographed the more essential parts. 

 In one instance a pamphlet was bor- 

 rowed from Europe for this purpose. 



For the exact measurement of col- 

 onies, etc., a strip of plate glass 35 cm. 

 long and ruled into 350 mm. spaces 

 may be had from Carl Zeiss, and will 

 be found very convenient (fig. 102). 



vSteel rules of any size and of very 

 excellent workmanship, graduated ac- 

 cording to the English or the metric 

 system in any degree of fineness, may 

 be had from the L,. S. Starrett Com- 

 pany, Athol, Mass. Two of these rules 

 much used by the writer are, respec- 

 tively, 12 inches and 30 centimeters 

 long. They are one inch wide and 

 about three sixty-fourths of an inch 

 thick. They are graduated on both 

 sides, the metric rule into centimeters, 

 millimeters, and one-half millimeters, 

 and the English into inches, halves, 

 quarters, eighths, sixteenths, thirty- 

 seconds, and sixty-fourths. 



Stage micrometers made by Zeiss 

 are recommended for the finer measure- 

 ments. These have i millimeter 

 divided into tenths, twentieths, and 

 Fig. 102.* one-hundredths very accurately. All 



the magnifications of microscopic 



objects figured in this book are recorded in terms of such a micrometer. After the 

 drawing has been made it is customary to substitute for the section-slide this stage 

 micrometer and throw the image of some portion of the ruled scale on the paper 



I 102. Green cucumber soft-rotted by Rat'illits arnidcae. Contents emptied out and skin 

 tilled uitb \\;iicr and so photographed, 3 days from date of inoculation, which was by means of a 

 few needle-pricks. The fruit was kept at about 25 C. The black bands are pencil marks on the 

 millimeter rule placed inside. The numerous small dark spots are denser bits of tissue which did 

 not wash free on rinsing out the sack with water. At the left drops of water may be seen oozing 

 through the skin and falling. Photograph, nearly natural size, by Townsend. 



