J, M. BEAL 157 



diameters of 2 cm. or more, and a height above the original cut surfaces 

 of 2-2.5 *^rn- Similar appearing tumors were induced on bean pods, 

 with roots developing from them also. 



Histological Details. — The cells of the epidermis and pericycle re- 

 sponded less actively than those of the other tissues. The cells of the 

 cortical parenchyma enlarged somewhat and those near the endodermis 

 became meristematic. The cells of the endodermis were highly responsive; 

 they were the first to show meristematic activity with nuclear divisions 

 being greatly accelerated shortly after treatment, and extending as far 

 as 5 cm. below the point of apphcation after a week. The derivatives 

 differentiated as phloem and xylem elements and large, apparently 

 multinucleate, parenchymatous cells. Many derivatives remained meri- 

 stematic while others gave rise to root histogens and eventually to 

 adventitious roots. Especially over the vascular bundles long proliferat- 

 ing strands of vascular tissues developed from endodermal derivatives. 

 These frequently enlarged sufficiently to rupture the tissues exterior 

 to them. The parenchyma of the primary phloem showed the same 

 general type of response and subsequent differentiation of tissues. Some 

 of the cells derived from it formed a part of the cortical tissues of the 

 apical crown of adventitious roots, A part of the tissues composing the 

 cortical portion of these adventitious roots, however, was derived from 

 the parenchyma of the secondary phloem. Other cells matured into 

 parenchymatous tissue, tracheids with simple pits, sieve tubes, and 

 companion cells. The cambium divided actively. Its derivatives often 

 remained active over long periods of time, later maturing as various 

 phloem or xylem elements, or continued as meristematic zones from 

 which such elements continued to form. 



Near the surface of application the cells of the rays adjacent to the 

 xylem proliferated greatly. Many of their derivatives matured as 

 tracheids, with meristematic areas intermingled with them. This con- 

 fused mass of tissue often persisted and continued development for 

 weeks. The ray cells adjacent to the phloem and just within the pericycle 

 also proliferated greatly and, in conjunction with the phloem cells 

 flanking them, gave rise to root histogens and also directly formed large 

 portions of the adventitious roots. 



The pith cells also proliferated greatly, with the first marked activity 

 adjacent to the surface of apphcation, but later activity progressed 

 down the stem next to the elements of the primary xylem. Large pitted 



