286 TAYLOR— ON THE PRODUCTION OF 



Ammonia. All stages in the formation of the pith cambium were 

 found, including, in the neighborhood of the wound, the formation of 

 xylem. Pith proliferations into the cavity also took place. 



Lithium Carbonate. The stages in the formation of the pith 

 cambium, including the formation of xylem, were seen as a result of the 

 injections made with this substance. Superficial proliferations also 

 occurred. 



Copper Sulphate. The pith cavity was much browned in this 

 series and the formation of a pith cambium occurred. 



Picric Acid. The formation of the pith cambium was active in 

 some of this series. When the injection was so severe as to kill a part 

 of the internode, extrafascicular cambia and bundles were produced. 



The Effect of the Injection on the General Growth of the Plant 



In order to fully appreciate the importance of the histological modi- 

 fications produced by the injections and by the attendant wounds, 

 it is necessary to consider the effect of these on the general health of the 

 plant. 



In general, unless the toxicity was quite high, there was no immediate 

 effect visible on the surface of the stem. When this was the case however, 

 the internode treated became flaccid. Later this effect extended up 

 and down the stem and death generally followed. If a violently corro- 

 sive substance had been injected the effect would have been even more 

 rapid. 



When the substance was only strong enough to have a locally toxic 

 effect, the first evidence of this effect was a browning around the injec- 

 tion holes. This gradually spread up and down the stem. This, in 

 time, might involve three or four internodes. 



The age of the shoot and its vigor at the time of the injection had 

 considerable to do with the effect of the injection. The more vigorous 

 and active the shoot the greater the spread of the injected fluid thru 

 the vascular system, and also the greater the response of the pith cells. 

 A stem that had not a vigorous habit tended to give a local reaction. 



Besides these local effects, due directly to the toxicity of the injected 

 substance, there was an effect on the growth of the injected internode 

 that occurred even tho the solution was so weak that tissue destruction 

 did not take place. 



This was first suspected when it was found that the injected internode 

 was shorter than those above and below it. Measurements were made 

 to determine to what degree this took place. The degree of variation 



