248. Photosynthesis in leaves, a. Pin two flat pieces of cork- 

 together over a portion of a suitable green leaf (to exclude light). 

 Place the plant in a bright place and leave two days. 1). Then pick 

 leaf; dip in boiling water for a minute or so; extract chlorophyll 

 with 95 f /f alcohol (some time will be necessary), and treat with 

 weak iodine solution. Note distribution of starch. Kxplanation? 

 c. Perform the same experiment with a leaf enclosed in a bottle 

 containing strong KOH to absorb CCX. The petiole is passed through 

 a slit in the cork and the whole closed airtight with vaseline. Note 

 difference from b? Explanation? d. Note distribution of starch 

 in a variegated leaf. Place the leaf (after momentary boiling) in 

 8o c /c alcohol to extract the chlorophyll and treat as before. Result? 

 Conclusion ? 



II. HOLOZOIC METABOLISM. 



The following study of certain) of the processes of metabolism 

 in a number of organisms will be carried on partly as laboratory 

 work, partly as seminary work. The processes are to be observed 

 by the student as far as possible. Where this is not possible, descrip- 

 tions of them are to be read, in the references that are given. The 

 essential point is to have after study a clear idea how the process 

 in question takes place ; be ready to describe and explain to the 

 instructor. The books and papers referred to will be placed on the 

 desk in the laboratory, and are to be referred to as a part of the 

 regular work. 



In organisms in general we can distinguish a number of factors 

 and processes concerned in metabolism. These are listed in the 

 following, together with suggestions for their study in the organisms 

 examined. 



a. The taking of food. Organs or processes involved. Make 

 sketches and descriptions if possible. 



Most organisms have either some process of bringing food to the 

 month, or of going to the food. Determine which is true in the 

 given case (or whether both or neither are true), and describe. 



b. The digestion of food. This usually takes place in an en- 

 closed region, the alimentary canal. Make a diagram of this when 

 possible. The processes involved are usually the subjection of the 

 food to certain chemicals. This is usually not directly observable, 

 but has been imitated experimentally. Such experiments we have 

 already carried on in our study of enzyme action. Sometimes the 

 changes in the food can be traced ; this should be done where possible. 



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