Polarity and regeneration in plants 
T. H. Morcan 
The earlier and greater development of the buds that stand at 
the distal end of a piece of a willow than of those that stand 
nearer to the base of the piece bears a certain general resemblance 
to the phenomenon of polarity in animals, and has led, in fact, to 
the use of the same word for both processes. This comparison 
needs, I think, to be more critically examined. During the past 
summer I have kept pieces of several plants, from which the leaves 
were removed, in a moist chamber with the lower end of the 
pieces in water, and have watched the development of the buds. 
In most cases, as in the willow, the more distal, though not neces- 
sarily the most distal, buds are the first to develop, and it could 
be easily seen that those that unfolded first were, as a rule, the 
largest and most advanced buds present on the piece when it was 
removed from the plant. In other words, the relative strength of 
the buds determines which develop first, and it seems most plausi- 
ble that in consequence of this development the other buds might 
be kept from unfolding because those that got the start used up 
all the available food substances that were present, or were being 
manufactured in the piece. It appears, therefore, that the result 
is not so much the outcome of the polarity of the piece, acting at 
the time of regeneration, as of preexisting conditions in the piece 
at the time of its removal from the plant. These determine which 
buds shall be the first to unfold. Whether or not this difference 
in the condition of the buds of the original piece has itself been 
regulated by polar relations in the growing point is a question for 
further consideration, but in any case it is one that does not involve 
the immediate question of the regeneration of the isolated piece. 
In one of the plants that I examined, the proximal and not the 
distal buds of the piece were the first to develop. It is this case 
that I wish more especially to discuss in connection with the prob- 
lem of polarity in plants. The plant was the common burdock, 
Arctium Lappa (Lappa officinalis). The leaves and the lateral 
ranches were cut off from half a dozen vigorous plants, and the 
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