Translocation of Flowering Hormones • 75 



right angles to each other. If all but two leaves (of different pairs) 

 are removed from the plant, and the lower is given short days and 

 the upper long days, several different results can be obtained. I! 

 the long-day leaf is in the same rank with (directly above) the 

 long-day leaf, flowering is prevented. If the long-day leaf is in the 

 rank opposite that of the short-day leaf, flowering is the same as if 



Fig. 5-2. Localization of flower- 

 ing stimulus in Kalanchoe. A single 

 leaf situated on the left-hand side 

 was repeatedly exposed to short 

 days whereas the rest of the plant 

 received long days. (Photograph 

 from Harder [1948], by permis- 

 sion of the company of Biologists, 

 Ltd., and courtesy of Dr. R. 

 Harder, University of Gottingen.) 



the long-day leaf were absent. Finally, if the long-day leaf is in 

 either of the two ranks at right angles to that of the short-day leaf, 

 some inhibition of flowering is evident. In this sort of experiment, 

 the transport of florigen is evidently upward from leaf to growing 

 point, but appropriately trimmed plants can be used for similar 

 studies on the transport downward from a short-day leaf to an 

 axillary shoot. Here again, a long-day leaf between the short-day 

 leaf and the shoot inhibits most effectively if it is in the same rank, 

 and least effectively if it is in the rank opposite. In short, whether 

 movement is up or down, the inhibition only occurs if the non- 

 induced leaf lies effectively between the induced leaf and the 

 growing point in question. This is apparently true for many plants 

 besides Kalanchoe and is again consistent with the postulated 

 movement of florigen with the carbohydrate stream. In addition, 



