t 



Part C. Propagation by Means of Cuttings from Underground Stems. 



6. In addition to having roots underground, a plant may have stems underground. This 

 is often true of grasses. Bermuda grass is a southern grass which spreads both by under- 

 ground and above ground stems, making a dense, thick sod which will stand a great deal of 

 tramping. In the South farmers often start lawns and pastures by planting these underground 

 stems in place of seeds. Most southern seed houses carry this material in stock, (a) Does the 

 underground stem of Bermuda grass resemble in any way the above ground stem of common 

 grasses, i. e., is there any evidence of nodes and leaves? (b) If leaves are present, how do 



' they differ from ordinary grass leaves? 



7. Underground stems are in some plants curiously modified. For instance, in the com- 

 mon potato the end of such a stem enlarges into a fleshy, rounded growth called a tuber. 



In general, the buds on the stems of plants arise from the axil of a leaf, (a) Since the 

 eye of the potato is essentially a bud, see if you can find anything, however scale-like and 

 tiny, about the eye which would correspond to the leaf, (b) Does the sweet potato have 

 eyes? (c) Explain your answer. 



8. Plants could be grown from the common potato just as from the sweet potato, but it 

 is not as profitable a method. The most profitable way is to cut the tuber into pieces having 

 from two to three eyes, and plant these in the garden or field directly. Plant such a piece in 

 a flower pot at a depth of two or three inches. 



Record results in the following order: 



(a) Date of planting, (b) Date of first appearance, (c) Time required to reach a height 

 of about three inches. 



9. Select a smooth potato about 3J4 inches in diameter. Count the number of eyes 

 Set the potato in a glass of water in such a position that the stem end will be about l / 2 inch 

 below the surface, leaving most of the eyes exposed to the air. Record data as follows: 

 (a) Number of eyes, (b) Time required to show evidence of sprouting, (c) Number of eyes 

 which produced vigorous sprouts, (d) Calculated per cent of eyes which produced plants. 



Part D. Propagation by Means of Grafting.* 



10. Most fruit trees are propagated by means of grafting, for the reason that trees prop- 

 agated by other methods give rise to fruit which is uncertain in kind and value. 



♦♦"Grafting is the operation of inserting a piece of plant into another plant with the inten- 

 tion that it shall grow. It differs from the making of cuttings in the fact that the severed 

 part grows in another plant rather than in the soil. There are two general kinds of graft- 

 ing — one which inserts a piece of branch in the stock (grafting proper), and one which inserts 

 only a bud with little or no wood attached (budding). In both cases the success of the opera- 

 tion depends on the growing together of the cambium of cion (or cutting) and that of the 

 stock. The cambium is the new and growing tissue lying underneath the bark and on the out- 

 side of the growing wood. Therefore, the line of demarcation between the bark and the wood 

 should coincide when the cion and stock are joined." 



Examine the cross section of a fresh willow twig — also the cross section of a fresh apple 

 twig, (a) Compare the cambium layer with the outer bar. (b) With wood, (c) Make a 

 drawing of the cross section of the apple twig one inch in diameter. Indicate the following 

 parts: Bark, cambium layer, wood, pith, (d) .What parts must be brought into close contact 

 in grafting? 



11. Of the several methods of grafting, root grafting is the one practiced with apples in 

 starting young trees. To illustrate the method of grafting in the laboratory, select a one-year- 

 old apple seedling for the root stock and an apple twig of last summer's growth for the cion. 



•If convenient, an opportunity should be given to study grafting in the field. 

 **From "Manual of Gardening," by L. H. Bail*". 



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