Chap. IU OF THE EADICLE OF THE BEAN. 143 



same maimer, and now eyery one of the radicles 

 became curved away from the cards, though one was 

 only slightly deflected. Some horticulturists believe 

 that certain kinds of seeds will not germinate pro- 

 perly in the middle of the winter, although kept at a 

 right temperature. If there really is any proper period 

 for the germination of the bean, the feeble degree of 

 sensibility of the above radicles may have resulted 

 from the trial having been made in the middle of the 

 winter, and not simply from the nights being too cold. 

 Lastly, the radicles of four beans, which from some 

 innate cause germinated later than all the others of 

 the same lot, and which grew slowly though appearing 

 healthy, were similarly tried, and even after 24 h. they 

 were hardly at all deflected from the attached cards 

 We may therefore infer that any cause which renders 

 the growth of the radicles either slower or more rapid 

 than the normal rate, lessens or annuls the sensibility 

 of their tips to contact. It deserves particular atten- 

 tion that when the attached objects failed to act, there 

 was no bending of any kind, excepting Sachs' curva- 

 ture. The force of our evidence would have been 

 greatly weakened if occasionally, though rarely, the 

 radicles had become curved in any direction inde- 

 pendently of the attached objects. In the foregoing 

 numbered paragraphs, however, it may be observed 

 that the extreme tip sometimes becomes, after a con- 

 siderable interval of time, abruptly curved towards the 

 bit of card ; but this is a totally distinct phenomenon; 

 as will presently be explained. 



Summary of the BesuUs of the foregoing EtperimentB 

 on tlie Badides of Viciafaba. — Altogether little squares 

 (about g-'ot^ of an inch), generally of sanded paper 

 as stiff as thin card (between '15 and '20 mm. in 

 thickness), sometimes of ordinary card, or little frag- 



