202 CIECUMNUTATION OF STEMS. Chap. IV 



were selected which, from being woody, or for other 

 reasons, seemed the least likely to circumnutate. The 

 observations and the diagrams were made in the 

 manner described in the Introduction. Plants in pots 

 were subjected to a proper temperature, and whilst 

 being observed, were kept either in darkness or were 

 feebly illuminated from above. They are arranged 

 in the order adopted by Hooker in Le Maout and 

 Decaisne's ' System of Botany.' The number of the 

 family to which each genus belongs is appended, as 

 this serves to show the place of each in the series. 



(1.) Iberit umbellata (Cruciferje, Fam. 14).— The movement of 

 the stem of a young plant, 4 inches in height, consisting of 

 four internodes (the hypoeotyl included) besides a large bud 



Fi?. 70. 



Iberis umheUata : circumnutation of stem of young plant, traced from 

 8.30 A.M. Sept. 13th to same hour on following morning. Distance of 

 summit of stem beneath the horizontal glass 7*6 inches. Diagram 

 I'educed to half of original size. Movement as here shown magniSel 

 between 4 and 5 times. 



on the summit, was traced, as here shown, during 21 h. 

 (Fig. 70). As far as we could judge the uppermost inch alone 

 of the stem circumnutated, and this in a simple manner. The 

 movement was slow, and the rate very unequal at different 

 times. In part of its course an irregular ellipse, or rather 

 triangle, was completed in 6 h. 30 m. 



(2.) Brassica oleracea (Cruciferse). — A very young plant, bearing 

 three leaves, of which the longest was only three-quarters of an 

 inch in length, was placed under a microscope, furnished with 

 an eye-piece micrometer and the tip of the largest leaf was 



