108 OIEOUMNUTATION OF HYPOOOTTLS, ETC. Chap. H, 



the extreme amount of movement from side to side 

 of their circumnutating stems was small; that of 

 the hypocotyl of Githago segetum was about '2 of an 

 inch, and that of Oucurbita ovifera about "28. A 

 very young shoot of Laihyrus nissolia moved about 

 •14, that of an American oak -2, that of the common 

 nut only '04, and a rather tall shoot of the Asparagus 

 •11 of an inch. The extreme amount of movement 

 of the sheath-like cotyledon of Plialaris Canariensis 

 was '3 of an inch ; but it did not move very quickly, 

 the tip crossing on one occasion five divisions of the 

 micrometer, that is, yj(jth of an inch, in 22 m. 5 s. A 

 seedling Nolana prostrata travelled the same distance 

 in 10 m. 38 s. Seedling cabbages circumutated much 

 more quickly, for the tip of a cotyledon crossed 

 1-^fth of an inch on the micrometer in 3 m. 20 s. ; and 

 this rapid movement, accompanied by incessant oscil- 

 lations, was a wonderful spectacle when beheld under 

 the microscope. 



The absence of light, for at least a day, does not 

 interfere in the least with the circumnutation of the 

 hypocotyls, epicotyls, or young shoots of the various 

 dicotyledonous seedlings observed by us ; nor with that 

 of the young shoots of some monocotyledons. The 

 circumnutation was indeed much plainer in darkness 

 than in light, for if the light was at all lateral the 

 stem bent towards it in a more or less zigzag course. 



Finally, the hypocotyls of many seedlings are drawn 

 during the winter into the ground, or even beneath it 

 so that they disappear. This remarkable process, 

 which apparently serves for their protection, has 

 been fully described by De Vries.* He shows that 



• ' Bot. Zeitung,' 1879, p. 649. burg,' Jahrg. xvi. p. 16, as quoted 

 See also Winkler in ' Verhandl. by Haberlandt, ' Schutzeinriuhun- 

 des Bot Vereins dor P. Bnuiden- gen der Keimpflanze,' 1877, p. 52 



