110 CIKCUMNUTATION OP COTYLEDONS. Chap. XI. 



cirled; so that ellipses, more or less narrow, were 

 described, and the cotyledons may safely be said to 

 haye circumnutated. Nor could this fact be accounted 

 for by the mere increase in length of the cotyledons 

 through growth, for this by itself would not induce 

 any lateral movement. That there was lateral move- 

 ment in some instances, as with the cotyledons of the 

 cabbage, was evident; for these, besides moving up 

 and down, changed their course from right to left 12 

 times in ]4 h. 15 m. With Solanum lycopersicum the 

 cotyledons, after falling in the forenoon, zigzagged 

 from side to side between 12 and 4 p.m., and then 

 commenced lising. The cotyledons of Lupinus luteus 

 are so thick (about '08 of an inch) and iieshy,* that 

 they seemed little likely to move, and were there- 

 fore observed with especial interest; they certainly 

 moved largely up and down, and as the line traced was 

 zigzag there was some lateral movement. The nine 

 cotyledons of a seedling Pinus pinaster plainly circum- 

 nutated ; and the figures described approached more 

 nearly to irregular circles than to irregular ovals or 

 ellipses. The sheath-like cotyledons of the Gra- 

 mineas circiimnutate, that is, move to all sides, as 

 plainly as do the hypocotyls or epicotyls of any dico- 

 tyledonous plants. Lastly, the very young fronds of 

 a Fern and of a Selaginella circumnutated. 



In a large majority of the cases which were care- 

 fully observed, the cotyledons sink a little downwards 

 in the forenoon, and rise a little in the afternoon or 

 evening. They thus stand rather more highly inclined 

 during the night than during the mid-day, at which 



* The cotyledons, though bright &o , 1877, p. 95), on the gradations 

 green, resemble to a certain ex- in the Leguniinosae between sub- 

 tent hypogean ones; see the in- aerial and subterranean cotvl» 

 teresting discus^ion by Haber- dons, 

 landt ('Die Sohutzcinrichtungen,' 



