CHAP. I. 



BRASSICA. 



19 



Fig. 9. 



vertically up and down all day long, and. as there was some 

 slight lateral movement, they circumnutated. 



The cabbage was one of the first plants, the seedlings of which 

 were observed by us, and we 

 did not then know how far 

 the circummitation of the 

 different parts was aifected 

 by light. Young seedlings 

 were therefore kept in com- 

 plete darkness except for- a 

 minute or two during each 

 observation, when they were 

 illuminated by a small wax 

 taper held almost vertically 

 above them. During the first 

 day the hypocotyi of one 

 changed its course 18 times 

 (see Fig. 9) ; and it deserves 

 notice that the longer axes 

 of the figures described often 

 cross one another at right or 

 nearly right angles. Another 

 seedling was observed in the 

 same manner, but it was 

 much older, for it had formed 

 a true leaf a quarter of an 

 inch in length, and the hy- 

 pocotyi was If inch in height. 

 The figure traced was a very 

 complex one, though the 

 movement was not so great 

 in extent as in the last case. 



The hypocotyi of another 

 seedling of the same age was 

 secured to a little stick, and 

 a filament having been fixed 

 to the midrib of one of the 

 cotyledons, the movement of 

 the bead was traced during 14 h. 15m. (see Fig. 10) in darkness. 

 It should be noted that the chief movement of the cotyledons, 

 namely, up and down, would be shown on a horizontal glass- 

 plate only by the lines in the direction of the midrib (that is, 



Brassica oleracea : circumnutation of 

 hypocotyi, in darkness, traced on a 

 horizontal glass, by means of a fila- 

 ment with a bead fixed across its 

 summit, between 9.15 A.M. and 

 8.30 A.M. on the following morn- 

 ing. Figure here reduced to one- 

 half of original scale. 



