RESPIRATION AND FERMENTATION 



129 



stration purposes is described by REED in the Journal of Applied Micros- 

 copy, 5, 1902, 1891. Yet another form and method, one having the great 

 educational advantage that every stage in the experimenting is visible to the 

 eye, while at the same time the apparatus is simple, portable, and convenient 

 of manipulation, is supplied by 

 my new demonstration respi- 

 rometer, described in the Bo- 

 tanical Gazette, 43, 1907, 274. 

 It is supplied among my normal 

 apparatus (page 46) and is 

 constructed as follows: 



The instrument (Fig. 33) 

 consists of three parts. First 

 is the oval chamber for the 

 seeds, with a water-bulb at the 

 bottom and a ground stopper 

 having an air-opening match- 

 ing with one in the neck. 

 Second is the measuring-cylin- 

 der in open communication 

 with the chamber, graduated 

 from 75 cc. to 100 cc. of the 

 combined capacity of itself and 

 chamber, though the 75-cc. 

 mark is actually placed at 77 

 cc. of the capacity. Third, 

 and communicating with the 

 preceding through a slender 

 rubber tube, is the reservoir 

 cylinder, ungraduated but with 

 index marks 25 cc. apart. Both 

 tubes are supported vertically 

 by any convenient laboratory 

 clamps which permit the reser- 

 voir tube to be slipped up and 

 down. For demonstration pur- 

 poses it is best to select seeds 

 in which the oxygen absorbed 

 and the carbon dioxide released 

 are as nearly as possible equal 

 in volume, e.g., Oats. Ten of 

 these of average size are 

 soaked, or, better, are selected 

 from a lot which have been 

 started in a germinator until the roots are about 5 mm. long; they are then 

 placed in the chamber, root ends down, just above the bulb, where they will 

 stick if previously wetted. These occupy approximately i cc. of volume, 



FIG. 33. RESPIEOMETER; Xf. 

 Explanation in text. 



