CHAP. III. OF THE RADICLE OF ZEA. 177 



case in which the deflection was 49, the two squares 

 had accidentally come into contact on one side of the 

 apex, and thus formed a lateral gable ; and the deflec- 

 tion was directed in part from this gable and in part 

 from the thick paper. In three cases alone the radicles 

 were not affected by the difference in thickness of the 

 squares of paper attached to their tips, and conse- 

 quently did not bend away from the side bearing the 

 stiffer paper. 



Zea mays : Sensitiveness of the apex of the Radicle to 

 contact. A large number of trials were made on this 

 plant, as it was the only monocotyledon on which we 

 experimented. An abstract of the results will suffice. 

 In the first place, 22 germinating seeds were pinned to 

 cork-lids without any object being attached to their 

 radicles, some being exposed to a temperature of 65-- 

 66 F., and others to between 74 and 79 ; and none of 

 them became curved, though some were a little inclined 

 to one side. A few were selected, which from having 

 germinated on sand were crooked, but when suspended 

 in damp air the terminal part grew straight down- 

 wards. This fact having been ascertained, little squares 

 of the card -like paper were affixed with shellac, on 

 several occasions, to the tips of 68 radicles. Of these 

 the terminal growing part of 39 became within 24 h. 

 conspicuously curved away from the attached squares 

 and from the perpendicular ; 13 out of the 39 forming 

 hooks with their points directed towards the zenith, 

 and 8 forming loops. Moreover, 7 other radicles out 

 of the 68, were slightly and two doubtfully deflected 

 from the cards. There remain 20 which were not 

 affected ; but 10 of these ought not to be counted ; 

 for one was diseased, two had their tips quite sur- 

 rounded by shellac, and the squares on 7 had slipped 

 so as to stand parallel to the apex, instead of obliquely 



