272 TA\"LOR— ON THE PRODUCTION OF 



stated that she had no desire to institute further experiments to investi- 

 gate the meristematic power of plant tissues, it was suggested by Dr. 

 Macfarlane that the work be continued by the writer, to which Dr. 

 Rumbold agreed. Work was begun about the first of April 1916, and 

 sufficient material having accumulated to pe;rmit the drawing of just 

 conclusions, there is here presented a summary of the experiments 

 carried on by the writer during the past year. The writer is greatly 

 indebted to Dr. John M. Macfarlane for suggesting this work, and for 

 his constant supervision and encouragement while it was in progress. 



Past studies of tissue abnormalities have been largely concerned 

 with wound-healing, gall-formation and so forth. The literature on 

 this subject has been admirably condensed by Kiister (1), The ma- 

 jor part of the work has been concerned with the general ability 

 to produce protective wound tissue, rather than to observe the capabilities 

 of change of each particular type of cell. 



The most extensive tissue-production seems to have been obtained 

 by Simon (5) from the ends of twigs of Populus nigra kept in a water- 

 saturated atmosphere. Pustular outgrowths on leaves have been re- 

 ported, and also similar intumescences on stems. The mesophyll of 

 the leaves seems in the first case to have been the active layer. Methods 

 of reproducing these experimentally have been found by Kiister and 

 others, and Erwin F. Smith (6) has published a paper on the production 

 by simple chemical means of tumor-like outgrowths that extends this 

 line of investigation. In addition to producing superficial outgrowths, 

 he caused internal pith proliferations in the stems, these developing 

 internal vascular structures. His experiments on this particular line 

 he states to have been begun in June 1916. Schilberszky (4) by mechan- 

 ical means produced extrafascicular bundles in Phaseolus. This showed 

 that there existed in the layer of cells outside of the hard-bast tissue 

 formative powers that under extraordinary conditions might be used 

 by the plant to furnish itself with additional vascular tissue. These 

 cortical cells that gave rise to the meristem were primary tissue, not 

 secondary tissue derived from a cambium. On the contrary, the cells 

 which developed the xylem studied by Dr. Rumbold in Castanea were 

 soft-bast cells in secondary or metaphloem derived from a cambium. 

 This is one important difference between the two conditions; another 

 is the comparative age of the tissues involved in the two plants. It 

 would generally be considered that the cells in the bark of a woody 

 perennial, (in some of the cases observed several years old), would be 

 far less responsive than those of an annual. 



