NEW CELL FORMATIONS IN PLANTS 293 



sections, which must be carefully distinguished from the abnormally 

 formed xylem. They were formed from the pith cells by simple lignifica- 

 tion, this occurrence, tho not normal to the species used, being nothing 

 unusual. It was most apparent in a plant of Polygonum that had had 

 a large part of the internode exposed to the air by the corroding action 

 of Picric Acid introduced in the solid form. 



The formation of phloem was not as clearly shown as was the forma- 

 tion of xylem. The cells inside of the cambium region were all so uni- 

 form in appearance (the cells formed by the original segmentation of 

 the pith cells are to be carefully distinguished here) that there seems 

 to be little if any true phloem present in the sections examined. It 

 may be that a httle longer time for maturation would have shown that 

 some of the questionable regions were really phloem. The formation 

 of phloem in this manner has already been reported for Ricinus, (6), 

 by Dr. Erwin F. Smith, who also reports the formation of "concentric 

 medullary bundles" in the pith. The writer is disinclined to assert 

 that this pith-cambium is a true bundle cambium on the basis of his 

 own preparations. 



Herbaceous Plants — Stimmary 



In order to obtain material that would serve to aid in the interpre- 

 tation of the conditions present near the wounds in the trunks of 

 Castanea, experiments were started on herbaceous plants. 



These mainly consisted of the injection into the pith cavity by means 

 of a hypodermic syringe, of various substances in aqueous solution. 

 The injections served to stunt the growth of the injected internode. 



Modifications in the tissues of the plant were produced both as a direct 

 action of the chemical agent as a stimulating agent, and indirectly as 

 a result of its toxic action on the cells. 



The reactions that can be considered as primarily due to the first 

 cause consisted mainly of prohferations into the pith cavity of the cells 

 bordering on it. 



Those due to the poisonous action of the injected fluid cannot always 

 be clearly distinguished from these, nor can they always be distinguished 

 from wound tissue reactions caused by the insertion of the injection 

 needle. 



As a result of the action of one or more of these agencies proliferations 

 of all the tissues except the epidermis and the lignified elements were 

 produced. 



