10 CIECUMNUTATION OF SEEDLINGS. Chap. I 



CHAPTEE I. 



The Cibc cmntjtating Movemekts of Seedling Plants. 



Cras.'ica oleracea, ciroumnutation of the radicle, of the arched hypo- 

 cotyl wlillst still buried beneath the ground, whilst rising above tlie 

 ground and straightening itself, and when erect — Circumnutation 

 of the cotyledons — Eale of movement — Analogous observations on 

 various organs in species of Githago, Gossypium, Oxalis, Tro- 

 psBolura, Citrus, iEsoulus, of several Leguminous and Ouourbita- 

 ceous genera, Opuntia, Helianthus, Primula, Cyclamen. Stapela, 

 Cerinthe, Nolana, Solanum, Beta, Eicinus, Querous, Corylus, Pinus, 

 Cyeas, Canna, Allium, Asparagus, Phalaris, Zea, Avena Nephro- 

 ' dium, and Selagiuella. 



The following chapter is devoted to the circum- 

 nutating movements of the radicles, hypocotyls, and 

 cotyledons of seedling plants; and, when the coty- 

 ledons do not rise above the ground, to the movements 

 of the epicotyl. But in a future chapter we shall have 

 to recur to the movements of certain cotyledons which 

 sleep at night. 



Brassica okracca {CTuc^fer(E). — Fuller details will be given 

 ■with respect to the movements in this case than in any other, 

 as space and time will thus ultimately be saved. 



liadicle. — A seed with the radicle projecting -05 inch was 

 fastened with shellac to a little plate of zinc, so that the 

 radicle stood up vertically; and a fine glass filament was then 

 fixed near its base, that is, close to the seed-coats. The seed 

 was surrounded by little bits of wet sponge, and the move- 

 ment of the bead at the end of the filament was traced (Fig. 1) 

 during sixty hours. In this time the radicle increased in 

 length from -05 to -11 inch. Had the filament been attached at 

 first close to the apex of the radicle, and if it could have re- 

 mained there all the time, the movement exhibited would have 



