1846 Journal of Applied Microscopy 



than are objects mounted in water or in aqueous media. Years of experience 

 with objectives in bright brass and nickel plated mounts, with the first case of 

 damage from heat not yet noted, indicates that, if reasonable care is taken, no 

 injury is to be feared from overheating. (7) A sub-stage condenser is recom- 

 mended in all instruments intended for use with medium and high power object- 

 ives. A plano-convex lens of about three-fourths inch focus is the most satisfactory 

 for use with the condensers described above. (8) If an ordinary microscope 

 with inclination joint is used in the place of a regular projection microscope, 

 great care must be taken in arranging the support so that the objective and body 

 will be in the optical axis of the mirror and condenser. This rule becomes 

 increasingly important when high-power objectives are used. 

 University of Chicago. A. H. COLE. 



METHODS IN PLANT PHYSIOLOGY. 



I. 



INTRODUCTORY. 



The present series of articles aims to deal exclusively with the technique of 

 laboratory work in Plant Physiology ; they are not designed to be a complete 

 outline of a course in physiological botany, nor a substitute for a laboratory 

 manual. Many of the historical methods with which all botanists are familiar 

 have been omitted except where improvements could be suggested. Although 

 these methods have been worked out for use in a university laboratory, yet many 

 of them on account of their simplicity or accuracy will be found suitable for ap- 

 plication in secondary schools. The illustrations are from photographs taken 

 by the author. Whatever value the methods may have is largely due to Profes- 

 sor F. C. Newcombe, of the University of Michigan, in whose laboratory they 

 have been developed. 



I. GROWTH. 



1. Dependence of Plants upon Oxygen for Growth. This fact is best demon- 

 strated by enclosing plants for several days in a chamber devoid of oxygen and 

 making comparisons with controls. Select two salt-mouth bottles about 15 cm. 

 high and prepare two strips of glass which will pass into the bottles and allow 

 the stoppers to be inserted. Cover one side of the glass with white blotting 

 paper, securing the end of the strip with a rubber band. Draw a heavy pencil 

 line across each strip of paper at least 2 cm. from one end, then saturate them 

 with water. Fasten two seedlings of peas (Pisum sativum) or lupine {Lupinus 

 albus) upon each strip by means of rubber bands, bringing the root-tips upon the 

 pencil line. Fill each bottle to a depth of .5 cm. with water which has been freed 

 from air by boiling, and insert the seedlings. Close one bottle with a perforated 

 stopper, allowing the seedlings to obtain atmospheric oxygen. Close the other 

 bottle with a two-perforate rubber stopper ; through one perforation pass a glass 

 tube to the bottom of the bottle and connect it with a hydrogen generator. Pass 

 a stream of pnre hydrogen through the bottle for thirty minutes, then plug the 

 open perforation in the stopper with a glass rod and fuse off the glass tube while 



