284 TAYLOR— ON THE PRODUCTION OF 



effect of the treatment was to produce a local breaking down of the 

 tissues, pith proUferations, and a proHferation of the cortical tissues 

 to form a wound callus. The Picric Acid was not solely responsible 

 for the tissue growths here, since similar and nearly equal growths oc- 

 curred in the control experiments, where the stems were merely punc- 

 tured with a dry needle. By means of serial celloidin sections the re- 

 lation of the wound to the tissues produced was followed out quite care- 

 fully in this plant. 



When these experiments were planned it was arranged that the largest 

 number should be done on Helianthus. In the late summer this plant 

 became so hard in the part near the ground that it was impossible to 

 obtain good, thin sections of it. Therefore it was possible to give much 

 of this material only a superficial examination. 



Gravity injections with Anilin Black showed the same conditions as 

 in Phytolacca. In the older stems the pitted vessels as well as the pro- 

 toxylem served for the conduction of the fluid. 



The main injections were made with Picric Acid, and in one of the 

 experiments this produced a very active pith-cambium (Plate LXXVI, 

 Fig. 18 and Plate LXXVII, Fig. 23). 



The work on Ricinus was the most successful done during the summer 

 of 1916. This plant was found to be a favorable one by Erwin F. Smith 

 (6). The plants used were grown from seed listed by the dealer under the 

 names Ricinus borhoniensis arboreus, R. purpureus, and R. cambodgensis. 

 They were injected with Picric Acid both by the gravity and the needle 

 methods, the latter yielding highly interesting results. The solutions 

 in the latter case were injected into the internodal cavity and had their 

 greatest effect on the wall of the cavity. Some of the solutions did get 

 into the vessels, however, and caused decided changes in the tissues 

 surrounding them. 



The most notable features of the sections are, first, the well developed 

 cambium formed in the pith, and second, the proUferations around the 

 vascular bundles. Hardly less interesting are the proliferations of the 

 pith cells into the internodal cavity. While preparing a set of sections 

 of an uninjected stem, proliferations similar in character to those into 

 the pith cavity of the injected specimens were found, altho less in extent. 

 They were not accompanied by any evident wound to the stem, and possi- 

 bly show that artificial stimulation is not requisite for their production. 



A feature that was very prominent around the wound was the pro- 

 duction of cork. This was greater in amount than that normally pro- 

 duced at the base of the plant. The formation of the cork occurred 



