CHAP. I. 



CUCURBITA. 



39 



upwards, in which position geotropism would act at first with 

 little power. A filament was attached near to its base, and 

 projected at about an angle of 45 above the horizon. The 

 general course followed during the 11 hours of observation and 

 during the following night, is shown in the accompanying 

 diagram (Fig. 26), and was plainly due to geotropism ; but it 

 was also clear that the radicle circumnutated. By the next 

 morning the tip had curved so much downwards that the fila- 

 ment, instead of projecting at 45 above the horizon, was nearly 

 horizontal. Another germinating seed was turned upside down 

 and covered with damp sand ; and a filament was fastened to 

 the radicle so as to project at an angle of about 50 above the 

 horizon; this radicle was '35 of an inch in length and a little 

 curved. The course pursued was mainly governed, as in the 

 last case, by geotropism, but the line traced during 12 hours and 

 magnified as before was more strongly zigzag, again showing 

 circumnutation. 



Four radicles were allowed to grow downwards over plates 

 of smoked glass, inclined at 70 to the horizon, under the 



Fig. 27. 



A. B. 



Cucurbita ovifera : tracks 

 left by tips of radicles 

 in growing downwards 

 over smoked glass- 

 plates, inclined at 70 

 to the horizon. 



Cucurbita ovifera : circumnuta- 

 tion of arched hypocotyl at 

 a very early age, traced in 

 darkness on a horizontal glass, 

 from 8 A.M. to 10.20 A.M. on 

 the following day. The move- 

 ment of the bead magnified 

 20 times, here reduced to one- 

 half of original scale. 



same conditions as in the cases of JEsculus, Phaseolus, and 

 Vicia. Facsimiles are here given (Fig. 27) of two of these 

 track's ; and a third short one was almost as plainly serpentine 

 as that at A. It was also manifest by a greater or less amount 

 of soot having been swept off the glasses, that the tips had 

 3 



