186 WATER CULTURE, PHOTOSYNTHESIS, RESPIRATION. 



(i.e. in which some portions of the leaf are devoid of 

 chlorophyll) ; the Japanese Maple, or variegated kinds of 

 Ivy, Coleus, Abutilon, or Geranium, answer well. Sketch 

 each leaf before it is decolorised and tested, and observe 

 that only the green parts produce starch. 



(6) Get five wide-mouthed bottles, with tightly fitting corks. 

 Wash each bottle out with water, to keep the air inside it moist, 

 and label them A , B, C, D, E. Leave A empty, to serve as a check 

 or " control." Into B and C put some living green leaves ; into Z>, 

 some green leaves which have been killed by boiling ; into E, some 

 pieces of living wood cut from a branch, or some roots, or mush- 

 rooms, or any other living but not green tissue. Charge the bottles 

 with carbon dioxide by breathing into each several times. Another 

 plan is to pour into each jar some "plain soda-water" from a syphon 

 (a convenient method is to use a Sparklet syphon, charging it with- 

 out adding soda); the "soda-water" is of course simply water 

 charged with carbon dioxide. Cork each bottle tightly, smearing 

 the edges of the corks with vaseline. Place bottle B in the dark, 

 the others in the light, for a whole day. Then test each bottle for 

 carbon dioxide by pouring in a little lime-water and seeing whether 

 it turns milky. 



Try the experiments several times, and record your results, with 

 the inferences to be drawn from them. If carefully carried out, 

 these experiments will show (1) that living green leaves absorb 

 carbon dioxide from the air in sunlight ; (2) that they do not absorb 

 it in darkness ; (3) that dead leaves do not absorb carbon dioxide ; 

 (4) that living but not green parts of plants do not absorb it. 



(c) Repeat the observations on the giving-off of oxygen by water- 

 plants, but put into the water, along with the water-plant, pieces of 

 living roots and of mushrooms. Do these living but not green 

 tissues give off oxygen? If any gas-bubbles escape from them, do 

 they come off in light only, or in darkness as well ? 



247. The General Properties of Chlorophyll should 

 be studied, with special reference to its absorption spec- 

 trum. The best materials for this purpose are thin, fairly 

 young, clear-green leaves ; a good typical spectrum is given 

 by alcoholic extract of leaves of Grasses, Primrose, Tro- 

 paeolum, etc. Fine fluorescence is shown by extract of 

 leaves of Ivy and Cineraria. 



(a) Almost any leaves may be used, and it would be 

 interesting to compare, with the spectroscope, chlorophyll 

 from the leaves of various plants, including those with 



