EXERCISE 35 

 SOME EXAMPLES OF EXTENSIVE STORAGE OF FOODS 



Materials. Tubers of potato or Jerusalem artichoke ; bulbs of 

 onion or hyacinth ; some carrots, parsnips, turnips, sweet potatoes, 

 or radishes; eosin; iodine; Fehling's solution ; Millon's reagent. 



Directions for work. 1. Cut open a tuber and test several 

 parts of the interior for stored foods, using the tests with which 

 you are familiar from preceding exercises. Does food material 

 appear to be relatively abundant ? Is it generally distributed 

 throughout the tuber ? What kind of food material appears to 

 be most abundant ? In textbooks of human physiology or 

 home economics look up the composition of the potato, noting 

 especially the proportion of proteins and carbohydrates. Do 

 your conclusions correspond to the analysis given? Why are 

 potatoes a valuable article of food for men ? What use is made 

 of the stored food by the potato plant? 



Tubers are said to be very much thickened stems. Can you 

 prove or disprove this ? Examine the exterior of the tuber for 

 such features as you found on stems (Exercise 34). Are there 

 buds present, as indicated by their readiness to grow into new 

 shoots and by budlike structure (Exercises 31, 32) ? Can you 

 identify the terminal bud ? Is there anything which corresponds 

 to leaves ? Review the previous exercises, or the textbook, to 

 refresh your mind regarding the exact position of leaves with 

 relation to buds, and note that as the tuber is underground, 

 any leaves found upon it might differ very much from ordinary 

 foliage leaves. 



To determine the location of fibrovascular tissues, cut off 

 a slice of the tuber at the opposite end from the terminal 

 bud and stand the tuber on the cut end in red ink or eosin 

 solution. After twenty-four hours cut cross and longitudinal 

 sections and trace the fibrovascular bundles. Can you trace 

 the fibrovascular bundles out to the structures suspected of 

 being buds ? 



2. Examine a bulb for stored food as the tuber was examined, 

 using the outline and questions given under 1. 



[42] 



