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XXXIII. 



SOME RESEAKCHES IN EXPERIMENTAL MORPHOLOGY. 



(1). On thk Change of the Petioi.k into a Strm 



BY MEANS OF GraFTTNG. 



By JOSEPH DOYLE, B.A., M.Sc, 

 Assistant in the Biological Laboratoi\y, University College, Dublin. 



(Pi.ATES XXYIII-XXXIV.) 



[cOMMUNICATRn BY PROFESSOR J. BAYLEY BCITLER, M.A., M.B.] 

 [Bead December 15, 19H, Published Maeoh 24, 1915.] 



I. — Introduction. 

 The following is an account of certain attempts made to ascertain if the petiole 

 of a plant can be made to function as a stem, and to study any anatomical 

 changes that may take place. The differences between the petiole and the 

 stem are well known. The differences are essential, and would almost seem 

 to prevent tbe former ever taking on the function, not to mention the form, 

 of the latter. Thus the petiole has limited growth, and usually a very 

 restricted length of life. Coupled with this limited growtli and length of 

 life, we find that the cambium loses its activity as soon as the leaf has 

 reached its full size, so we never find in the petiole that well-developed 

 secondary growth so characteristic of the stem. Finally, the development of 

 periderm — except pathologically — is in far and away the vast majority of 

 plants entirely absent from the petiole. It is these differences that lend the 

 interest to the work. 



The attempt has been made by other workers, but in only one instance in 

 any detail, and then by a method different from that adopted in this paper. 



The question as to whether the petiole can function as a stem was answered 

 by Knight (1) as long ago as 1803 in a positive manner. Thus Knight grafted 

 a sprout on a petiole of a vino plant. The graft took, the scion grew well, 

 attaining a height of 9 feet to 10 feet. The petiole in the autumn, he notes, 

 had developed wood below the graft. He gives no further details. 



Carriere — quoted by De Vries (2) — rooted leaves of the orange. He 

 grafted small sprouts on the petiole at the base of the lamina. The sprouts 



SCIENT. PROG. B.D.S, , VOL. XIV., NO, XXXIII. 3 U 





