Chap. I. 



VICIA. 



29 



Fig. 18. 



the tracks varitd in breadth. The more perfectly serpentine 

 tracks made by the radicles of Phaseolus muUiflorus and Vicia 

 faba (presently to be described), render 

 it almost certain that the radicles of 

 the present plant circnmnntated. 



Phaseolus muUiflorus (LeguminoEse). 

 — Four smoked glass-plates were ar- 

 ranged in the same manner as des- 

 cribed tinder .aisculus, and the tracks 

 left by the tips of four radicles of the 

 present plant, whilst growing down- 

 wards, were photographed as trans- 

 parent objects. Three of them are 

 here exactly copied (Fig. 19). Their 

 serpentine courses show that the tips 

 moved regularly from side to side; 

 they also pressed alternately with 

 greater or less force on the plates, 

 sometimes rising up and leaving them 

 altogether for a very short distance ; 

 but this was better seen on the 

 original plates than in the copies. 

 These radicles therefore were continually moving in all direc- 

 tions — that is, they circumnutated. The distance between the 

 extreme right and left positions 

 of the radicle A, in its lateral 

 movement, was 2 mm., as ascer- 

 tained by measurement with an 

 eye-piece micrometer. 



Vicia faba (Common Bean) 

 (Leguminosse). — Radicle. — Some 

 beans were allowed to germinate 

 on bare sand, and .after one had 

 protruded its radicle to a length 

 of "2 of an inch, it was turned 

 upside down, so that the radicle, 

 which was kept in damp air, 

 now stood upright. A filament, 

 nearly an inch in length, was 

 affixed obliquely near its tip; and the movement of the 

 terminal bead was traced from 8.30 a.m. to 10.30 p.m., as shown 

 La Fig. 18. The radicle at first changed its course twice 



A. B. 



^•culus h'ppocastnnum : out- 

 lines of tracks left on in- 

 clined glass-plates by ti|)» 

 of radicles. In A the plate 

 was inclined at 70° with 

 the honzon, and the radicle 

 was 1 ■ 9 inch in length, and 

 •23 inch in diameter at base. 

 In B the plate was inclined 

 65° with the horizon, and 

 the radicle was a trifle 

 larger. 



Fig. 19. 



V. 



A. B. C. 



Phaseolus muUiflorus : tracks left 

 on inclined smoked glass-plates 

 by tips of radicles in growing 

 downwards. A and C, plates 

 inclined at 60°, B inclined at 

 68° with the horizon. 



