and Laboratory Methods. 1847 



the hydrogen is running. (The fusion will be facilitated if the glass tube has 

 been previously drawn out in one place to about half the standard diameter.) 

 After twenty-four to forty-eight hours compare the amount of growth in the 

 different seedlings. 



2. Minimum, Optimum and Maximum Temperature for Growth. This im- 

 portant experiment requires but little in the way of apparatus for its successful 

 performance if the preparations are carefully watched and the temperature not 

 allowed to vary more than two degrees. Prepare seven culture jars or damp 

 chambers, using for this purpose small glass jars (pint fruit cans answer well), 

 having the inside lined with moist filter paper and the mouth closed with a cover 

 of wood or cork, through which a thermometer is passed. Arrange the jars 

 about the laboratory in places where the temperatures given below are found to 

 be fairly constant. If there is a paraffin oven or incubator in the laboratory the 

 higher temperatures can be obtained around and upon it ; or construct a tempo- 

 rary shelf with one end near a register or radiator and arrange the jars along 

 the shelf at distances which will give the desired temperatures. Make a small 

 table for holding the seedlings in the following manner : cut a disk of sheet 

 cork or thin lumber a little smaller than the mouth of the jar, insert three legs 

 about 10 cm. long and bore five gimlet holes through the disk. Soak this table 

 in water for three or four hours before using. 



When ready to set up the experiment, place water to a depth of 1 cm. in the 

 damp chambers, take corn {Zea Mais) or pea (Pisum sativum) seedlings of 3 to 5 

 cm. length and mark them with a drop of India ink applied with a fine brush 1 

 cm. from the tip of the root. Place the seedlings in the holes in the tables and 

 place the tables in the damp chambers inunediately. The chambers now need 

 the continuous attention of one or two students in order to maintain constant 

 temperatures (the work will be facilitated if the temperature of the room be kept 

 constant). The chambers containing pea seedlings should be kept at tempera- 

 tures of 8°, 20°, 22.5°, 25°, 30°, 35°, 40°C; those containing corn seedlings 

 should be kept at 8°, 25°, 30°, 32.5°, 35°, 40°, 45°C. At the end of five to 

 seven hours remove the five seedlings from each chamber and accurately meas- 

 ure the distance from the tip to the ink mark ; average the measurements and 

 record the amount of growth at the several temperatures ; determine the mini- 

 mum, optimum and maximum for each plant. 



3. To Determine the Distribution of Growth in Stems and Leaves. Use 

 young potted plants for this experiment and keep them under the most favorable 

 conditions possible. Mark at intervals of 2 mm. the terminal three or four ex- 

 posed internodes of the stem of a -monocotyledon and also of a dicotyledon. 

 The common Wandering Jew {Tradescantiafluminensis') is the most satisfactory 

 monocotyledon for this experiment ; the leaf-sheaths should be removed on one 

 side to permit the marking of the stem throughout the full length of the inter- 

 nodes. The Periwinkle vine ( Vinca major) is a very satisfactory dicotyledon for 

 marking, as it grows well in the laboratory ; only the shorter shoots should be 

 used. 



Mark also two or three immature leaves on each of these plants, covering 

 the lower surface of the leaf with ink dots 2 mm. apart, both longitudinally and 

 transversely. Make observations after three or four days to determine the place 

 and amount of growth. 

 University of Michigan, ' HOWARD S. Reed. 



