86 THE FLOWERING PROCESS 



movement of the flowering stimulus from one plant to another. 

 Epidermal and cortical tissue is removed from the stems of two 

 plants, usually with a razor blade. These exposed areas are then 

 pressed together, and the two stems are tied in place. Wide rubber 

 bands may be used, although care should be taken not to wrap them 

 too tightly. Special tapes and other materials are also available. 



A more difficult procedure involves the grafting of a leaf from one 

 plant onto another plant. The leaf is removed with a razor blade, 

 usually taking some stem tissue along with the leaf and its petiole 

 (in some cases it may be desirable to specifically exclude the bud in 

 the axil of the leaf). This is then attached to a portion of stem from 

 which the epidermal and some cortical tissues have been removed, 

 as in approach grafting. Again the leaf is held in place by binding 

 with rubber bands or special tape. The problem in leaf grafting is 

 that the leaf tends to wilt. It will be 3 to 4 days before anatomical 

 connections are made between the leaf and the stem so that the leaf 

 can obtain sufficient moisture from the plant to which it is grafted. 

 We found that we could successfully keep grafted leaves alive by 

 putting them under a fine water spray or mist. If the spray system 

 is turned on for a few seconds each minute, nearly all of the grafts 

 are successful. Enclosing in plastic bags is another way of keeping 

 grafted leaves or shoots from wilting. 



5. The Notebook 



The data listed in Table 5-3 should be recorded in connection with 

 every experiment. Often interpretation makes it necessary to go back 

 and check data which perhaps did not seem important at the time of 

 recording. 



IV. The Measurement of Flowering 



1. The Problem 



There are many steps between the vegetative plant and the mature 

 flower, and this may strongly influence the way flowering is measured. 

 The interests of the researcher will usually determine the method of 

 measurement. If, as in the agricultural or horticultural sciences, one 

 is primarily concerned with ultimate flowering, then the method of 

 measurement is of relatively small consequence. The problem 



