NEW CELL FORMATIONS IN PLANTS 279 



would cause a rupture of the cells between them, unless these kept pace 

 with this growth. This occurs in part by cell multiplication, but mainly 

 by cell growth, and is followed by lignification. 



Before passing to the closing phase of development the stone-cells 

 may be mentioned. They were found in various locations in normal 

 and in transforming bark, and they were seen in the patches of hgnifying 

 phloem, but not in the xylem patches forming in the phloem. They had 

 no evident relation to these. The hard-bast strands were much dislo- 

 cated, and sometimes were broken by the unequal growth of adjacent 

 xylem-patches, but otherwise they were unmodified. 



In time there arises a new bundle-cambium from soft-bast cells 

 outside of the abnormal xylem areas. Unless there was something 

 of this sort formed, there would be no means for growth to continue 

 other than by the extension in number and size of the abnormal patches, 

 and there would be no phloem formed in these regions. Instead of 

 this happening, a meristematic zone arises on the outer face of hard- 

 bast strands and having essentially the same origin as the xylem-cambia 

 described above. This zone in time forms xylem and phloem (Plate 

 LXXIII, Fig. 8) of the type ordinarily seen on the sides of a wound. 

 Whether there originates first a xylem-cambium of the extraordinary 

 type, which later becomes a bundle-cambium, or whether there is phloem 

 formed from the first as well as xylem, the material at hand failed to show. 

 Following the establishment of this new bundle-cambium, natural growth 

 progressed as usual. There is a peculiarity of the hard-bast formed 

 by this cambium (at least during the first year or two) that is also charac- 

 teristic of that formed by the rapidly dividing cambium on the edges of 

 a wound. The abnormal strands of hard-bast are not flat and regularly 

 disposed, nor are they formed as in normal tissue, one ring each year, 

 they are larger and round in transverse section, and are somewhat scat- 

 tered (Plate LXXIV, Fig. 12). This, in the normal type of wound, is 

 shown in the second figure of Dr. Rumbold's paper (3). 



The abnormal development of cork-cambia that was reported by 

 Dr. Rumbold seems, in all cases that the writer has examined, to be 

 about what might have been expected. These cork layers cause the 

 shelUng oflf of bark which is seen around all wounds, and eventually 

 over all parts of the trunk of the tree. They also occur isolated in the 

 bark, and here are probably due, not so much to the injection, as to 

 mechanical injuries. They may possibly be due to, and surround, Uttle 

 internal splits caused by strains set up by the deeper furrowing of the 

 bark. An interesting phenomenon seen in one case was the stimulation 



