158 SENSITIVENESS OF THE APEX CHAP. III. 



analogous cases will be immediately described. The 

 fact is here mentioned because it was a striking spec- 

 tacle, showing the difference in the sensitiveness of 

 the radicle in different parts, to behold in the same 

 jar one set of radicles curved away from the squares on 

 their tips, and another set curved towards the squares 

 attached a little higher up. Moreover, the kind of 

 curvature in the two cases is different. The squares 

 attached above the apex cause the radicle to bend 

 abruptly, the part above and beneath remaining nearly 

 straight ; so that here there is little or no transmitted 

 effect. On the other hand, the squares attached to 

 the apex affect the radicle for a length of from about 

 4 to even 8 mm., inducing in most cases a sym- 

 metrical curvature ; so that here some influence is 

 transmitted from the apex for this distance along the 

 radicle. 



Pisum sativum (var. Yorkshire Hero) : Sensitiveness of 

 the apex of the Radicle. Little squares of the same card- 

 like paper were affixed (April 24th) with shellac to 

 one side of the apex of 10 vertically suspended radicles : 

 the temperature of the water in the bottom of the jars 

 was 60-61 F. Most of these radicles were acted on 

 in 8 h. 30 m. ; and eight of them became in the course 

 of 24 h. conspicuously, and the remaining two slightly, 

 deflected from the perpendicular and from the side 

 bearing the attached squares. Thus all were acted on ; 

 but it will suffice to describe two conspicuous cases. 

 In one the terminal portion of the radicle was bent at 

 right angles (A, Fig. 66) after 24 h. ; and in the other 

 (B) it had by this time become hooked, with the apex 

 pointing to the zenith. The two bits of card here used 

 were '07 inch in length and '04 inch in breadth. Two 

 other radicles, which after 8 h. 30 m. were moderately 

 deflected, became straight again after 24 h. Another 



