GRAFTING AND REGENERATION 177 



fered with. At times an incomplete union took place between the 

 parts ; at others, even though the first union was perfect, death later 

 ensued. 



On the other hand, when similar pieces were grafted with their 

 original orientation, a perfect union took place and the piece became 

 a part of the stock. The results establish, Vochting claims, that 

 every part and every portion of a part has a polar orientation in one 

 direction, and furthermore, in a body having a radially symmetrical 

 form, there is also a radial polarization; that is, the inner side of 

 each part is different from the outer side of the same surface, even 

 though no such difference is apparent to us. The properties of the 

 tissue-complex rest, in the last analysis, on that of the cells ; the 

 properties of the whole being only the sum total of the properties of 

 its elements, so that we may say that every living cell of the root 

 is polarized, not only longitudinally, but also radially ; each has a 

 different apical and root pole, a different anterior and posterior pole, 

 and also right and left polar relations. These results, deduced from 

 the experiments in grafting, lead Vochting to formulate the follow- 

 ing rule : " Like poles repel, unlike poles attract." This rule is the 

 same as the law of the magnet. In fact, Vochting states that the 

 root and the stem relations show a remarkable resemblance, despite 

 many differences, to a magnet. If the magnet is broken into pieces 

 it may be reunited by bringing unlike poles together, but not by unit- 

 ing like poles ; the same statement holds for the root and the stem. 



Exception may be taken, I believe, to parts of Vochting's conclu- 

 sions, especially in the light of the recent experiments in grafting in 

 animals. It is by no means to be granted without further demonstra- 

 tion that the properties of the whole organism are only the sum- 

 total of the action of the individual cells. If, as seems to be the case, 

 the cells are organically united into a whole, the properties of this 

 whole may be very different from the sum of the properties of the 

 individual cells, just as the properties of sugar are entirely different 

 from the sum of the properties of carbon, hydrogen, and oxygen. 



The statement that like poles repel and unlike poles attract is, I 

 believe, a conclusion that goes beyond the evidence. The experi- 

 ments show that like poles do often unite in plants, and this has 

 been abundantly shown to be the case in the lower animals, and even 

 in forms as high as the earthworm and the tadpole. Even if when like 

 poles are united subsequent changes take place, that in some cases, 

 although apparently not in animals, lead to the death of the graft, it 

 by no means follows that this has anything to do with the attraction 

 or repulsion of the parts, but rather with some difficulty in obtaining 

 food, or with the transportation of substances through the plant. In 

 the lower animals we have seen that when like poles are united 



