Chap. IV. CIECUMNUTATION OF STEMS. 211 



must have moved in a plane at right angles to that of the lateral 

 movement, that is, it must have circumnutated. On the next day 

 (6th) the shoot moved in the course of 16 h. four times to the right, 

 and four times to the left; and this apparently represents the 

 formation of four ellipses, so that each was completed in 4 h. 



(17.) CeratophyHum demersum (CeratophyllejB, Fam. 220). — An 

 interesting account of the movements of the stem of this water- 

 plant has been published by M. E. Eodier.* The movements are 

 confined to the young internodes, becoming less and less lower 

 down the stem; and they are extraordinary from their amplitude. 

 The stems sometimes moved through an angle of above 2.0° in 

 6 h., and in one instance through 220° in 3 h. They generally 

 bent from right to left in the morning, and in an opposite direc- 

 tion in the afternoon ; but the movement was sometimes tempo- 

 rarily reversed or quite arrested. It was not affected by light. 

 It does not appear that M. Eodier made any diagram on a hori- 

 zontal plane representing the actual course pursued by the 

 apex, but he speaks of the " branches executing round their 

 axes of growth a anovement of torsion." From the particulars 

 above given, and remembering in the case of twining plants and 

 of tendrils, how difficult it is not to mistake their bending to all 

 points of the compass for true torsion, we are led to believe that 

 the stems of this CeratophyHum circumnutate, probably in the 

 shape of narrow ellipses, each completed in about 26 h. The 

 following statement, however, seems to indicate something 

 different from' ordinary circumnutation, but we cannot fnlly 

 understand it. M. Eodier says : " II est alors facile de voir que 

 ]e mouvement de flexion se produit d'abord dans les merithalles 

 superieurs, qu'il se propage ensuite, en s'amoindrissant du hunt 

 en has; tandis quau contraire le mouvement de redressemevt 

 commence par la partie inferieure pour se terminer h la partie 

 superieure qui, quelquefois, pen de temps avant de se relcver 

 tout a fait, forme avec I'axe un angle tres aigu." 



(18 ) GonifercB. — Dr. Maxwell Masters states (' Journal Linn 

 Soc.,' Doc. 2nd, 1879) that the leading shoots of many Coniferas 

 during the season of their active growth exhibit very remark- 

 able movements of revolving nutation, that is, they circumnu- 

 tate. We may feel sure that the lateral shoots whilst growing 

 would exhibit the same movement if carefully observed. 



» 'Cnmptes Eendua,' April 3ntli. 1877. Also a second liutios 

 published separately in Bouidi-aux, Nov. 12th, 1877. 



