NEW CELL FORMATIONS IN PLANTS 299 



Fig. 22. This shows a type of proliferation in Ricinus that involves young meta- 

 xj'lem as well as pith. Below "w.v" is showTi metaxylem that has not 

 been affected. Compare with Plate LXXVIII Fig. 29. X 45. 



Fig. 23. The Xylem Formed from the Pith Cambium in Ilclianlhus. From Injec- 

 tion No. 7, treated with 1:100 Picric Acid. The character of the pitted 

 vessels formed from the pith-cambium is hard to show. The wall of a 

 pitted vessel is shown at "^." X 85. 



Fig. 24. Proliferation of a Large ^lass of Cells in Polygonum. From Injection No. 

 19, treated with NIL OH 10% Solution. This shows that not only can the 

 superficial cells proliferate singly or in small groups, but large masses of 

 deep-lying cells can act together and form nodules on the sides of the 

 cavity. X 17. 



PLATE LXXVni— THE FORMATION OF THE EXTRAFASCICULAR BUN- 

 DLES IN POLYGONUM— ALSO PROLIFERATIONS AROUND 

 THE PROTOXYLEM AND CORK FOR- 

 MATION IN RICINUS 



Fig. 25. The First Stage in the Formation of the Extrafascicular Bundle. From 

 Injection No. 23, see above. There are seen here the first cell walls laid 

 down in the formation of an extra-fascicular bundle. Note especially 

 "a." X55. 



Fig. 26. A Well Developed Extrafascicular Cambium, Polygonum. From Injection 

 No. 23, see above. The cambium shown here had just begun to lay down 

 wood when the specimen was cut. There is seen a pitted vessel at 



"b." X55. 



Fig. 27. Extra-fascicular Bundle in Polygonum. This shows one of the most advanced 

 cases that these experiments have produced. A large group of pitted 

 vessels is shown at "d." X 70. 



Fig. 28. Cork Formation in Ricinus. From Injection lb, for data see Injection la, 

 above. This photograph shows the manner of cork formation in Ricinus. 

 The interest attaches to the manner in which the different layers of the 

 collenchymatous outer cortex take part in the process. The needle hole 

 was above the top of the picture. It is easy to see the individual layers of 

 cells, as "a," "b," "d," along the lower margin of the field, and to trace 

 each row upward and determine what part it had in the formation of the 

 cork-cambium. The position of this cambium is along "/"-"/. " It will 

 be noted that the nearer the region under observation is to the puncture, the 

 deeper are the layers that take part in the cork formation. X 45. 



Fig. 29. An Advanced Case of Proliferation in Ricinus. From Injection 2c, treated 

 with Picric Acid 1:100 G.M. The tissue destruction here was much more 

 considerable than in the preceeding case. Considerable numbers of 

 dark conglomerate crystals are seen that are located in a tissue that must 

 have come from the cambium, either directly or by proliferation of cells 

 previously formed from it. The cambium had resumed normal growth, 

 and the normal metaxylem is seen near the lower part of the picture. X 20. 



