8 8 REGENERA TION 



the region of the old plant from which the leaf has been taken. 

 Sachs discovered in 1893 that when the leaves of the begonia are 

 taken from a plant in bloom, the adventitious buds that develop from 

 the leaves very quickly produce new flowers. If the leaves are taken 

 from a plant that has not yet produced flowers, the new plant that 

 develops from the leaf does not produce flowers until after a much 

 longer time. Goebel repeated the experiment with achimenes, and 

 found that the new plants that develop from leaves from the flower- 

 ing part of the stem (Fig. 36) produce flowers sooner than do the 

 plants that develop from leaves from the base of the same plant. 

 The former produce, as a rule, only one or two leaves and the flower 

 stalk ; the latter, a large number of leaves. 



Sachs explains these results as due to a flower-forming stuff that 

 is supposed to be present in the leaves when the plant is about to 

 blossom. This material is supposed to act on the new plant that 

 develops from the leaves, and to bring it sooner to maturity. Goebel 

 points out that the result may also be explained by the fact that the 

 leaves in the flowering region may be poorer in food materials and, 

 in consequence, the adventitious buds that they produce are weaker, 

 and, as experience has shown in other cases, a weakening of the 

 tissues brings about more quickly the formation of flowers. Never- 

 theless, Goebel inclines to Sachs' hypothesis of specific or formative 

 stuffs, without, however, denying that there is also an inner polarity 

 or "disposition" that also appears in the phenomena of regeneration. 

 But Goebel seems to think that the phenomena of polarity "can 

 most easily be brought under a common point of view by means of 

 Sachs" assumption that there are different kinds of stuffs that go to 

 make the different organs. In the normal life of the plant shoot- 

 forming stuffs are carried to the vegetative points, while root-forming 

 materials go to the growing ends of the roots. In consequence, 

 when a piece is cut off and the flow of the formative stuffs is inter- 

 rupted, the root-forming stuff will accumulate at the base of the 

 piece and the shoot-forming stuffs at the apex. In the leaf the flow 

 of all formative substances is toward the base of the leaf, and it is 

 in this region that the new plants arise after the removal of the leaf." 

 A confirmation of this point of view, Goebel believes, is furnished by 

 the following cases. Some monocotyledonous plants seldom set seed 

 because the vegetative organs, the bulbs, tubers, etc., that reproduce 

 the plant, exert a stronger attraction upon the building stuff than 

 do the young seeds. 1 Lindenmuth has shown in some of these 

 forms that pieces of the stem produce, near the base, numerous 

 bulblets, because the building stuff moves toward the base. In 

 Hyacinthiis orientalis, on the other hand, bulblets are produced at 



1 Examples of this are found in Lilium candidum, Lachenalia luteola. 



