NEW CELL FOR^LVTIONS IN PLANTS 297 



in such a photograph as this, they are too similar in color to the surrounding 

 soft-bast. In the photograph "c" is just outside the region of the re- 

 formed cambium. A little below and to the right of "c" there is a lighter 

 patch separated from the .\ylem by a dark line, and other smaller patches 

 are to be seen in similar positions. These are hard-bast patches corres- 

 ponding to "g" of Plate LXXIV, Fig. 12. The included hard-bast strands 

 are marked "d" and "e." The group of hard-bast strands of which "e" 

 is a part is not of the same appearance as the more normal shaped ones 

 {"d") farther out. This irregularity was caused by an injury to the 

 cambium prececding the removal of the blight infection, which subsequent 

 operation in turn caused the formation of the .\ylcm cambia. From "/" 

 downward is wood formed from the old cambium before its growth was 

 stopped. X 11. 



Fig. 12. General View of a Transformed Area. It is verj- difficult to show the complex 

 details of the transformed areas in a low-power photograph. In the illus- 

 tration all above "//" is normal phloem. Just below " li" there is a 

 little local disturbance of the growth. The reformed bundle-cambium 

 stretches across the picture between the phloem and the somewhat darker 

 x>'lem. Just outside of it are located ("g") the hard-bast patches formed 

 from this cambium. At "j" is the row of hard-bast strands outside of 

 which the new bundle-cambium started activity. At "i" is the only 

 hard-bast ring which had formed outside of it the temporary xylem-cambia. 

 X 14. 



KEY TO THE LETTERING OF THE FIGURES OF THE HERBACEOUS 



PLANTS 



(Other signs than these are explained in the individual descriptions.) 



"cp" ParenchjTna of Cortex "mx" Metaxylem of Wood 



"hb" Hard-bast of Phloem "/>" Pith 



PLATE LXXV— THE PITH CA:MBIUM IN POLYGONUM 



The first two of these figures hardly need any explanation: they show the pith 

 region just bordering on the ca\aty, and the increase in the number of the cell walls 

 laid down in the formation of the pith-cambium. The description of this process 

 is given on page 292. 



Fig. 13. First Stages in the Formation of the Pith Cambium. From Injection No. 

 3, where Picric Acid was introduced in solid form into the treated internode. 

 X 55. 



Fig. 14. Well Formed Pith Cambium. From in jection No. 1, Distilled Water. X 55. 

 Fig. 15. This is a general \aew of one of the pith regions and part of the bundle ring 



in Injection No. 1, and shows the point of entrance of the injection needle. 



The letters "f"^"f" mark the position of the pith cambium. X 9. 



